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857 lines
34 KiB
C++
857 lines
34 KiB
C++
/*
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* jquant1.c
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*
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* Copyright (C) 1991-1995, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains 1-pass color quantization (color mapping) routines.
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* These routines provide mapping to a fixed color map using equally spaced
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* color values. Optional Floyd-Steinberg or ordered dithering is available.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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#ifdef QUANT_1PASS_SUPPORTED
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/*
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* The main purpose of 1-pass quantization is to provide a fast, if not very
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* high quality, colormapped output capability. A 2-pass quantizer usually
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* gives better visual quality; however, for quantized grayscale output this
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* quantizer is perfectly adequate. Dithering is highly recommended with this
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* quantizer, though you can turn it off if you really want to.
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*
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* In 1-pass quantization the colormap must be chosen in advance of seeing the
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* image. We use a map consisting of all combinations of Ncolors[i] color
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* values for the i'th component. The Ncolors[] values are chosen so that
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* their product, the total number of colors, is no more than that requested.
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* (In most cases, the product will be somewhat less.)
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*
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* Since the colormap is orthogonal, the representative value for each color
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* component can be determined without considering the other components;
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* then these indexes can be combined into a colormap index by a standard
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* N-dimensional-array-subscript calculation. Most of the arithmetic involved
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* can be precalculated and stored in the lookup table colorindex[].
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* colorindex[i][j] maps pixel value j in component i to the nearest
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* representative value (grid plane) for that component; this index is
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* multiplied by the array stride for component i, so that the
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* index of the colormap entry closest to a given pixel value is just
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* sum( colorindex[component-number][pixel-component-value] )
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* Aside from being fast, this scheme allows for variable spacing between
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* representative values with no additional lookup cost.
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*
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* If gamma correction has been applied in color conversion, it might be wise
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* to adjust the color grid spacing so that the representative colors are
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* equidistant in linear space. At this writing, gamma correction is not
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* implemented by jdcolor, so nothing is done here.
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*/
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/* Declarations for ordered dithering.
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*
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* We use a standard 16x16 ordered dither array. The basic concept of ordered
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* dithering is described in many references, for instance Dale Schumacher's
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* chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
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* In place of Schumacher's comparisons against a "threshold" value, we add a
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* "dither" value to the input pixel and then round the result to the nearest
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* output value. The dither value is equivalent to (0.5 - threshold) times
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* the distance between output values. For ordered dithering, we assume that
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* the output colors are equally spaced; if not, results will probably be
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* worse, since the dither may be too much or too little at a given point.
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*
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* The normal calculation would be to form pixel value + dither, range-limit
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* this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
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* We can skip the separate range-limiting step by extending the colorindex
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* table in both directions.
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*/
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#define ODITHER_SIZE 16 /* dimension of dither matrix */
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/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
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#define ODITHER_CELLS ( ODITHER_SIZE * ODITHER_SIZE ) /* # cells in matrix */
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#define ODITHER_MASK ( ODITHER_SIZE - 1 ) /* mask for wrapping around counters */
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typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
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typedef int ( *ODITHER_MATRIX_PTR )[ODITHER_SIZE];
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static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
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/* Bayer's order-4 dither array. Generated by the code given in
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* Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
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* The values in this array must range from 0 to ODITHER_CELLS-1.
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*/
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{ 0, 192, 48, 240, 12, 204, 60, 252, 3, 195, 51, 243, 15, 207, 63, 255 },
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{ 128, 64, 176, 112, 140, 76, 188, 124, 131, 67, 179, 115, 143, 79, 191, 127 },
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{ 32, 224, 16, 208, 44, 236, 28, 220, 35, 227, 19, 211, 47, 239, 31, 223 },
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{ 160, 96, 144, 80, 172, 108, 156, 92, 163, 99, 147, 83, 175, 111, 159, 95 },
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{ 8, 200, 56, 248, 4, 196, 52, 244, 11, 203, 59, 251, 7, 199, 55, 247 },
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{ 136, 72, 184, 120, 132, 68, 180, 116, 139, 75, 187, 123, 135, 71, 183, 119 },
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{ 40, 232, 24, 216, 36, 228, 20, 212, 43, 235, 27, 219, 39, 231, 23, 215 },
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{ 168, 104, 152, 88, 164, 100, 148, 84, 171, 107, 155, 91, 167, 103, 151, 87 },
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{ 2, 194, 50, 242, 14, 206, 62, 254, 1, 193, 49, 241, 13, 205, 61, 253 },
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{ 130, 66, 178, 114, 142, 78, 190, 126, 129, 65, 177, 113, 141, 77, 189, 125 },
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{ 34, 226, 18, 210, 46, 238, 30, 222, 33, 225, 17, 209, 45, 237, 29, 221 },
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{ 162, 98, 146, 82, 174, 110, 158, 94, 161, 97, 145, 81, 173, 109, 157, 93 },
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{ 10, 202, 58, 250, 6, 198, 54, 246, 9, 201, 57, 249, 5, 197, 53, 245 },
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{ 138, 74, 186, 122, 134, 70, 182, 118, 137, 73, 185, 121, 133, 69, 181, 117 },
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{ 42, 234, 26, 218, 38, 230, 22, 214, 41, 233, 25, 217, 37, 229, 21, 213 },
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{ 170, 106, 154, 90, 166, 102, 150, 86, 169, 105, 153, 89, 165, 101, 149, 85 }
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};
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/* Declarations for Floyd-Steinberg dithering.
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*
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* Errors are accumulated into the array fserrors[], at a resolution of
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* 1/16th of a pixel count. The error at a given pixel is propagated
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* to its not-yet-processed neighbors using the standard F-S fractions,
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* ... (here) 7/16
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* 3/16 5/16 1/16
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* We work left-to-right on even rows, right-to-left on odd rows.
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*
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* We can get away with a single array (holding one row's worth of errors)
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* by using it to store the current row's errors at pixel columns not yet
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* processed, but the next row's errors at columns already processed. We
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* need only a few extra variables to hold the errors immediately around the
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* current column. (If we are lucky, those variables are in registers, but
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* even if not, they're probably cheaper to access than array elements are.)
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*
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* The fserrors[] array is indexed [component#][position].
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* We provide (#columns + 2) entries per component; the extra entry at each
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* end saves us from special-casing the first and last pixels.
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*
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* Note: on a wide image, we might not have enough room in a PC's near data
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* segment to hold the error array; so it is allocated with alloc_large.
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*/
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#if BITS_IN_JSAMPLE == 8
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typedef INT16 FSERROR; /* 16 bits should be enough */
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typedef int LOCFSERROR; /* use 'int' for calculation temps */
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#else
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typedef INT32 FSERROR; /* may need more than 16 bits */
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typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */
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#endif
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typedef FSERROR FAR * FSERRPTR; /* pointer to error array (in FAR storage!) */
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/* Private subobject */
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#define MAX_Q_COMPS 4 /* max components I can handle */
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typedef struct {
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struct jpeg_color_quantizer pub;/* public fields */
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/* Initially allocated colormap is saved here */
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JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */
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int sv_actual; /* number of entries in use */
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JSAMPARRAY colorindex; /* Precomputed mapping for speed */
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/* colorindex[i][j] = index of color closest to pixel value j in component i,
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* premultiplied as described above. Since colormap indexes must fit into
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* JSAMPLEs, the entries of this array will too.
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*/
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boolean is_padded; /* is the colorindex padded for odither? */
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int Ncolors[MAX_Q_COMPS];/* # of values alloced to each component */
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/* Variables for ordered dithering */
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int row_index; /* cur row's vertical index in dither matrix */
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ODITHER_MATRIX_PTR odither[MAX_Q_COMPS];/* one dither array per component */
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/* Variables for Floyd-Steinberg dithering */
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FSERRPTR fserrors[MAX_Q_COMPS];/* accumulated errors */
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boolean on_odd_row; /* flag to remember which row we are on */
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} my_cquantizer;
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typedef my_cquantizer * my_cquantize_ptr;
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/*
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* Policy-making subroutines for create_colormap and create_colorindex.
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* These routines determine the colormap to be used. The rest of the module
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* only assumes that the colormap is orthogonal.
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*
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* * select_ncolors decides how to divvy up the available colors
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* among the components.
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* * output_value defines the set of representative values for a component.
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* * largest_input_value defines the mapping from input values to
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* representative values for a component.
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* Note that the latter two routines may impose different policies for
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* different components, though this is not currently done.
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*/
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LOCAL int
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select_ncolors( j_decompress_ptr cinfo, int Ncolors[] ) {
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/* Determine allocation of desired colors to components, */
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/* and fill in Ncolors[] array to indicate choice. */
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/* Return value is total number of colors (product of Ncolors[] values). */
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int nc = cinfo->out_color_components;/* number of color components */
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int max_colors = cinfo->desired_number_of_colors;
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int total_colors, iroot, i, j;
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boolean changed;
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long temp;
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static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
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/* We can allocate at least the nc'th root of max_colors per component. */
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/* Compute floor(nc'th root of max_colors). */
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iroot = 1;
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do {
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iroot++;
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temp = iroot; /* set temp = iroot ** nc */
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for ( i = 1; i < nc; i++ ) {
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temp *= iroot;
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}
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} while ( temp <= (long) max_colors );/* repeat till iroot exceeds root */
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iroot--; /* now iroot = floor(root) */
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/* Must have at least 2 color values per component */
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if ( iroot < 2 ) {
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ERREXIT1( cinfo, JERR_QUANT_FEW_COLORS, (int) temp );
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}
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/* Initialize to iroot color values for each component */
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total_colors = 1;
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for ( i = 0; i < nc; i++ ) {
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Ncolors[i] = iroot;
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total_colors *= iroot;
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}
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/* We may be able to increment the count for one or more components without
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* exceeding max_colors, though we know not all can be incremented.
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* Sometimes, the first component can be incremented more than once!
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* (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
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* In RGB colorspace, try to increment G first, then R, then B.
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*/
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do {
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changed = FALSE;
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for ( i = 0; i < nc; i++ ) {
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j = ( cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i );
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/* calculate new total_colors if Ncolors[j] is incremented */
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temp = total_colors / Ncolors[j];
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temp *= Ncolors[j] + 1;/* done in long arith to avoid oflo */
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if ( temp > (long) max_colors ) {
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break;
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} /* won't fit, done with this pass */
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Ncolors[j]++; /* OK, apply the increment */
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total_colors = (int) temp;
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changed = TRUE;
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}
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} while ( changed );
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return total_colors;
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}
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LOCAL int
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output_value( j_decompress_ptr cinfo, int ci, int j, int maxj ) {
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/* Return j'th output value, where j will range from 0 to maxj */
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/* The output values must fall in 0..MAXJSAMPLE in increasing order */
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/* We always provide values 0 and MAXJSAMPLE for each component;
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* any additional values are equally spaced between these limits.
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* (Forcing the upper and lower values to the limits ensures that
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* dithering can't produce a color outside the selected gamut.)
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*/
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return (int) ( ( (INT32) j * MAXJSAMPLE + maxj / 2 ) / maxj );
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}
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LOCAL int
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largest_input_value( j_decompress_ptr cinfo, int ci, int j, int maxj ) {
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/* Return largest input value that should map to j'th output value */
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/* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */
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/* Breakpoints are halfway between values returned by output_value */
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return (int) ( ( (INT32) ( 2 * j + 1 ) * MAXJSAMPLE + maxj ) / ( 2 * maxj ) );
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}
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/*
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* Create the colormap.
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*/
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LOCAL void
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create_colormap( j_decompress_ptr cinfo ) {
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my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
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JSAMPARRAY colormap; /* Created colormap */
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int total_colors; /* Number of distinct output colors */
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int i, j, k, nci, blksize, blkdist, ptr, val;
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/* Select number of colors for each component */
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total_colors = select_ncolors( cinfo, cquantize->Ncolors );
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/* Report selected color counts */
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if ( cinfo->out_color_components == 3 ) {
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TRACEMS4( cinfo, 1, JTRC_QUANT_3_NCOLORS,
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total_colors, cquantize->Ncolors[0],
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cquantize->Ncolors[1], cquantize->Ncolors[2] );
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} else {
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TRACEMS1( cinfo, 1, JTRC_QUANT_NCOLORS, total_colors );
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}
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/* Allocate and fill in the colormap. */
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/* The colors are ordered in the map in standard row-major order, */
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/* i.e. rightmost (highest-indexed) color changes most rapidly. */
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colormap = ( *cinfo->mem->alloc_sarray )
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( (j_common_ptr) cinfo, JPOOL_IMAGE,
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(JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components );
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/* blksize is number of adjacent repeated entries for a component */
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/* blkdist is distance between groups of identical entries for a component */
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blkdist = total_colors;
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for ( i = 0; i < cinfo->out_color_components; i++ ) {
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/* fill in colormap entries for i'th color component */
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nci = cquantize->Ncolors[i];/* # of distinct values for this color */
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blksize = blkdist / nci;
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for ( j = 0; j < nci; j++ ) {
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/* Compute j'th output value (out of nci) for component */
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val = output_value( cinfo, i, j, nci - 1 );
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/* Fill in all colormap entries that have this value of this component */
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for ( ptr = j * blksize; ptr < total_colors; ptr += blkdist ) {
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/* fill in blksize entries beginning at ptr */
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for ( k = 0; k < blksize; k++ ) {
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colormap[i][ptr + k] = (JSAMPLE) val;
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}
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}
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}
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blkdist = blksize; /* blksize of this color is blkdist of next */
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}
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/* Save the colormap in private storage,
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* where it will survive color quantization mode changes.
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*/
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cquantize->sv_colormap = colormap;
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cquantize->sv_actual = total_colors;
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}
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/*
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* Create the color index table.
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*/
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LOCAL void
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create_colorindex( j_decompress_ptr cinfo ) {
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my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
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JSAMPROW indexptr;
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int i, j, k, nci, blksize, val, pad;
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/* For ordered dither, we pad the color index tables by MAXJSAMPLE in
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* each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
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* This is not necessary in the other dithering modes. However, we
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* flag whether it was done in case user changes dithering mode.
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*/
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if ( cinfo->dither_mode == JDITHER_ORDERED ) {
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pad = MAXJSAMPLE * 2;
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cquantize->is_padded = TRUE;
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} else {
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pad = 0;
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cquantize->is_padded = FALSE;
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}
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cquantize->colorindex = ( *cinfo->mem->alloc_sarray )
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( (j_common_ptr) cinfo, JPOOL_IMAGE,
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(JDIMENSION) ( MAXJSAMPLE + 1 + pad ),
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(JDIMENSION) cinfo->out_color_components );
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/* blksize is number of adjacent repeated entries for a component */
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blksize = cquantize->sv_actual;
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for ( i = 0; i < cinfo->out_color_components; i++ ) {
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/* fill in colorindex entries for i'th color component */
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nci = cquantize->Ncolors[i];/* # of distinct values for this color */
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blksize = blksize / nci;
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/* adjust colorindex pointers to provide padding at negative indexes. */
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if ( pad ) {
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cquantize->colorindex[i] += MAXJSAMPLE;
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}
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/* in loop, val = index of current output value, */
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/* and k = largest j that maps to current val */
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indexptr = cquantize->colorindex[i];
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val = 0;
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k = largest_input_value( cinfo, i, 0, nci - 1 );
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for ( j = 0; j <= MAXJSAMPLE; j++ ) {
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while ( j > k ) {/* advance val if past boundary */
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k = largest_input_value( cinfo, i, ++val, nci - 1 );
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}
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/* premultiply so that no multiplication needed in main processing */
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indexptr[j] = (JSAMPLE) ( val * blksize );
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}
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/* Pad at both ends if necessary */
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if ( pad ) {
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for ( j = 1; j <= MAXJSAMPLE; j++ ) {
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indexptr[-j] = indexptr[0];
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indexptr[MAXJSAMPLE + j] = indexptr[MAXJSAMPLE];
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}
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}
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}
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}
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/*
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* Create an ordered-dither array for a component having ncolors
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* distinct output values.
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*/
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LOCAL ODITHER_MATRIX_PTR
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make_odither_array( j_decompress_ptr cinfo, int ncolors ) {
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ODITHER_MATRIX_PTR odither;
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int j, k;
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INT32 num, den;
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odither = (ODITHER_MATRIX_PTR)
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( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF( ODITHER_MATRIX ) );
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/* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
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* Hence the dither value for the matrix cell with fill order f
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* (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
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* On 16-bit-int machine, be careful to avoid overflow.
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*/
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den = 2 * ODITHER_CELLS * ( (INT32) ( ncolors - 1 ) );
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for ( j = 0; j < ODITHER_SIZE; j++ ) {
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for ( k = 0; k < ODITHER_SIZE; k++ ) {
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num = ( (INT32) ( ODITHER_CELLS - 1 - 2 * ( (int)base_dither_matrix[j][k] ) ) )
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* MAXJSAMPLE;
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/* Ensure round towards zero despite C's lack of consistency
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* about rounding negative values in integer division...
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*/
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odither[j][k] = (int) ( num < 0 ? -( ( -num ) / den ) : num / den );
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}
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}
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return odither;
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}
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/*
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* Create the ordered-dither tables.
|
|
* Components having the same number of representative colors may
|
|
* share a dither table.
|
|
*/
|
|
|
|
LOCAL void
|
|
create_odither_tables( j_decompress_ptr cinfo ) {
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
ODITHER_MATRIX_PTR odither;
|
|
int i, j, nci;
|
|
|
|
for ( i = 0; i < cinfo->out_color_components; i++ ) {
|
|
nci = cquantize->Ncolors[i];/* # of distinct values for this color */
|
|
odither = NULL; /* search for matching prior component */
|
|
for ( j = 0; j < i; j++ ) {
|
|
if ( nci == cquantize->Ncolors[j] ) {
|
|
odither = cquantize->odither[j];
|
|
break;
|
|
}
|
|
}
|
|
if ( odither == NULL ) {/* need a new table? */
|
|
odither = make_odither_array( cinfo, nci );
|
|
}
|
|
cquantize->odither[i] = odither;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Map some rows of pixels to the output colormapped representation.
|
|
*/
|
|
|
|
METHODDEF void
|
|
color_quantize( j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows ) {
|
|
/* General case, no dithering */
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
JSAMPARRAY colorindex = cquantize->colorindex;
|
|
register int pixcode, ci;
|
|
register JSAMPROW ptrin, ptrout;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
register int nc = cinfo->out_color_components;
|
|
|
|
for ( row = 0; row < num_rows; row++ ) {
|
|
ptrin = input_buf[row];
|
|
ptrout = output_buf[row];
|
|
for ( col = width; col > 0; col-- ) {
|
|
pixcode = 0;
|
|
for ( ci = 0; ci < nc; ci++ ) {
|
|
pixcode += GETJSAMPLE( colorindex[ci][GETJSAMPLE( *ptrin++ )] );
|
|
}
|
|
*ptrout++ = (JSAMPLE) pixcode;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
color_quantize3( j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows ) {
|
|
/* Fast path for out_color_components==3, no dithering */
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register int pixcode;
|
|
register JSAMPROW ptrin, ptrout;
|
|
JSAMPROW colorindex0 = cquantize->colorindex[0];
|
|
JSAMPROW colorindex1 = cquantize->colorindex[1];
|
|
JSAMPROW colorindex2 = cquantize->colorindex[2];
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for ( row = 0; row < num_rows; row++ ) {
|
|
ptrin = input_buf[row];
|
|
ptrout = output_buf[row];
|
|
for ( col = width; col > 0; col-- ) {
|
|
pixcode = GETJSAMPLE( colorindex0[GETJSAMPLE( *ptrin++ )] );
|
|
pixcode += GETJSAMPLE( colorindex1[GETJSAMPLE( *ptrin++ )] );
|
|
pixcode += GETJSAMPLE( colorindex2[GETJSAMPLE( *ptrin++ )] );
|
|
*ptrout++ = (JSAMPLE) pixcode;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize_ord_dither( j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows ) {
|
|
/* General case, with ordered dithering */
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex_ci;
|
|
int * dither; /* points to active row of dither matrix */
|
|
int row_index, col_index;/* current indexes into dither matrix */
|
|
int nc = cinfo->out_color_components;
|
|
int ci;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for ( row = 0; row < num_rows; row++ ) {
|
|
/* Initialize output values to 0 so can process components separately */
|
|
jzero_far( (void FAR *) output_buf[row],
|
|
(size_t) ( width * SIZEOF( JSAMPLE ) ) );
|
|
row_index = cquantize->row_index;
|
|
for ( ci = 0; ci < nc; ci++ ) {
|
|
input_ptr = input_buf[row] + ci;
|
|
output_ptr = output_buf[row];
|
|
colorindex_ci = cquantize->colorindex[ci];
|
|
dither = cquantize->odither[ci][row_index];
|
|
col_index = 0;
|
|
|
|
for ( col = width; col > 0; col-- ) {
|
|
/* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
|
|
* select output value, accumulate into output code for this pixel.
|
|
* Range-limiting need not be done explicitly, as we have extended
|
|
* the colorindex table to produce the right answers for out-of-range
|
|
* inputs. The maximum dither is +- MAXJSAMPLE; this sets the
|
|
* required amount of padding.
|
|
*/
|
|
*output_ptr += colorindex_ci[GETJSAMPLE( *input_ptr ) + dither[col_index]];
|
|
input_ptr += nc;
|
|
output_ptr++;
|
|
col_index = ( col_index + 1 ) & ODITHER_MASK;
|
|
}
|
|
}
|
|
/* Advance row index for next row */
|
|
row_index = ( row_index + 1 ) & ODITHER_MASK;
|
|
cquantize->row_index = row_index;
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize3_ord_dither( j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows ) {
|
|
/* Fast path for out_color_components==3, with ordered dithering */
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register int pixcode;
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex0 = cquantize->colorindex[0];
|
|
JSAMPROW colorindex1 = cquantize->colorindex[1];
|
|
JSAMPROW colorindex2 = cquantize->colorindex[2];
|
|
int * dither0; /* points to active row of dither matrix */
|
|
int * dither1;
|
|
int * dither2;
|
|
int row_index, col_index;/* current indexes into dither matrix */
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for ( row = 0; row < num_rows; row++ ) {
|
|
row_index = cquantize->row_index;
|
|
input_ptr = input_buf[row];
|
|
output_ptr = output_buf[row];
|
|
dither0 = cquantize->odither[0][row_index];
|
|
dither1 = cquantize->odither[1][row_index];
|
|
dither2 = cquantize->odither[2][row_index];
|
|
col_index = 0;
|
|
|
|
for ( col = width; col > 0; col-- ) {
|
|
pixcode = GETJSAMPLE( colorindex0[GETJSAMPLE( *input_ptr++ ) +
|
|
dither0[col_index]] );
|
|
pixcode += GETJSAMPLE( colorindex1[GETJSAMPLE( *input_ptr++ ) +
|
|
dither1[col_index]] );
|
|
pixcode += GETJSAMPLE( colorindex2[GETJSAMPLE( *input_ptr++ ) +
|
|
dither2[col_index]] );
|
|
*output_ptr++ = (JSAMPLE) pixcode;
|
|
col_index = ( col_index + 1 ) & ODITHER_MASK;
|
|
}
|
|
row_index = ( row_index + 1 ) & ODITHER_MASK;
|
|
cquantize->row_index = row_index;
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize_fs_dither( j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows ) {
|
|
/* General case, with Floyd-Steinberg dithering */
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register LOCFSERROR cur;/* current error or pixel value */
|
|
LOCFSERROR belowerr; /* error for pixel below cur */
|
|
LOCFSERROR bpreverr; /* error for below/prev col */
|
|
LOCFSERROR bnexterr; /* error for below/next col */
|
|
LOCFSERROR delta;
|
|
register FSERRPTR errorptr; /* => fserrors[] at column before current */
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex_ci;
|
|
JSAMPROW colormap_ci;
|
|
int pixcode;
|
|
int nc = cinfo->out_color_components;
|
|
int dir; /* 1 for left-to-right, -1 for right-to-left */
|
|
int dirnc; /* dir * nc */
|
|
int ci;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
JSAMPLE * range_limit = cinfo->sample_range_limit;
|
|
SHIFT_TEMPS
|
|
|
|
for ( row = 0; row < num_rows; row++ ) {
|
|
/* Initialize output values to 0 so can process components separately */
|
|
jzero_far( (void FAR *) output_buf[row],
|
|
(size_t) ( width * SIZEOF( JSAMPLE ) ) );
|
|
for ( ci = 0; ci < nc; ci++ ) {
|
|
input_ptr = input_buf[row] + ci;
|
|
output_ptr = output_buf[row];
|
|
if ( cquantize->on_odd_row ) {
|
|
/* work right to left in this row */
|
|
input_ptr += ( width - 1 ) * nc;/* so point to rightmost pixel */
|
|
output_ptr += width - 1;
|
|
dir = -1;
|
|
dirnc = -nc;
|
|
errorptr = cquantize->fserrors[ci] + ( width + 1 );/* => entry after last column */
|
|
} else {
|
|
/* work left to right in this row */
|
|
dir = 1;
|
|
dirnc = nc;
|
|
errorptr = cquantize->fserrors[ci];/* => entry before first column */
|
|
}
|
|
colorindex_ci = cquantize->colorindex[ci];
|
|
colormap_ci = cquantize->sv_colormap[ci];
|
|
/* Preset error values: no error propagated to first pixel from left */
|
|
cur = 0;
|
|
/* and no error propagated to row below yet */
|
|
belowerr = bpreverr = 0;
|
|
|
|
for ( col = width; col > 0; col-- ) {
|
|
/* cur holds the error propagated from the previous pixel on the
|
|
* current line. Add the error propagated from the previous line
|
|
* to form the complete error correction term for this pixel, and
|
|
* round the error term (which is expressed * 16) to an integer.
|
|
* RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
|
|
* for either sign of the error value.
|
|
* Note: errorptr points to *previous* column's array entry.
|
|
*/
|
|
cur = RIGHT_SHIFT( cur + errorptr[dir] + 8, 4 );
|
|
/* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
|
|
* The maximum error is +- MAXJSAMPLE; this sets the required size
|
|
* of the range_limit array.
|
|
*/
|
|
cur += GETJSAMPLE( *input_ptr );
|
|
cur = GETJSAMPLE( range_limit[cur] );
|
|
/* Select output value, accumulate into output code for this pixel */
|
|
pixcode = GETJSAMPLE( colorindex_ci[cur] );
|
|
*output_ptr += (JSAMPLE) pixcode;
|
|
/* Compute actual representation error at this pixel */
|
|
/* Note: we can do this even though we don't have the final */
|
|
/* pixel code, because the colormap is orthogonal. */
|
|
cur -= GETJSAMPLE( colormap_ci[pixcode] );
|
|
/* Compute error fractions to be propagated to adjacent pixels.
|
|
* Add these into the running sums, and simultaneously shift the
|
|
* next-line error sums left by 1 column.
|
|
*/
|
|
bnexterr = cur;
|
|
delta = cur * 2;
|
|
cur += delta;/* form error * 3 */
|
|
errorptr[0] = (FSERROR) ( bpreverr + cur );
|
|
cur += delta;/* form error * 5 */
|
|
bpreverr = belowerr + cur;
|
|
belowerr = bnexterr;
|
|
cur += delta;/* form error * 7 */
|
|
/* At this point cur contains the 7/16 error value to be propagated
|
|
* to the next pixel on the current line, and all the errors for the
|
|
* next line have been shifted over. We are therefore ready to move on.
|
|
*/
|
|
input_ptr += dirnc;/* advance input ptr to next column */
|
|
output_ptr += dir;/* advance output ptr to next column */
|
|
errorptr += dir;/* advance errorptr to current column */
|
|
}
|
|
/* Post-loop cleanup: we must unload the final error value into the
|
|
* final fserrors[] entry. Note we need not unload belowerr because
|
|
* it is for the dummy column before or after the actual array.
|
|
*/
|
|
errorptr[0] = (FSERROR) bpreverr;/* unload prev err into array */
|
|
}
|
|
cquantize->on_odd_row = ( cquantize->on_odd_row ? FALSE : TRUE );
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Allocate workspace for Floyd-Steinberg errors.
|
|
*/
|
|
|
|
LOCAL void
|
|
alloc_fs_workspace( j_decompress_ptr cinfo ) {
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
size_t arraysize;
|
|
int i;
|
|
|
|
arraysize = (size_t) ( ( cinfo->output_width + 2 ) * SIZEOF( FSERROR ) );
|
|
for ( i = 0; i < cinfo->out_color_components; i++ ) {
|
|
cquantize->fserrors[i] = (FSERRPTR)
|
|
( *cinfo->mem->alloc_large )( (j_common_ptr) cinfo, JPOOL_IMAGE, arraysize );
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Initialize for one-pass color quantization.
|
|
*/
|
|
|
|
METHODDEF void
|
|
start_pass_1_quant( j_decompress_ptr cinfo, boolean is_pre_scan ) {
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
size_t arraysize;
|
|
int i;
|
|
|
|
/* Install my colormap. */
|
|
cinfo->colormap = cquantize->sv_colormap;
|
|
cinfo->actual_number_of_colors = cquantize->sv_actual;
|
|
|
|
/* Initialize for desired dithering mode. */
|
|
switch ( cinfo->dither_mode ) {
|
|
case JDITHER_NONE:
|
|
if ( cinfo->out_color_components == 3 ) {
|
|
cquantize->pub.color_quantize = color_quantize3;
|
|
} else {
|
|
cquantize->pub.color_quantize = color_quantize;
|
|
}
|
|
break;
|
|
case JDITHER_ORDERED:
|
|
if ( cinfo->out_color_components == 3 ) {
|
|
cquantize->pub.color_quantize = quantize3_ord_dither;
|
|
} else {
|
|
cquantize->pub.color_quantize = quantize_ord_dither;
|
|
}
|
|
cquantize->row_index = 0;/* initialize state for ordered dither */
|
|
/* If user changed to ordered dither from another mode,
|
|
* we must recreate the color index table with padding.
|
|
* This will cost extra space, but probably isn't very likely.
|
|
*/
|
|
if ( !cquantize->is_padded ) {
|
|
create_colorindex( cinfo );
|
|
}
|
|
/* Create ordered-dither tables if we didn't already. */
|
|
if ( cquantize->odither[0] == NULL ) {
|
|
create_odither_tables( cinfo );
|
|
}
|
|
break;
|
|
case JDITHER_FS:
|
|
cquantize->pub.color_quantize = quantize_fs_dither;
|
|
cquantize->on_odd_row = FALSE;/* initialize state for F-S dither */
|
|
/* Allocate Floyd-Steinberg workspace if didn't already. */
|
|
if ( cquantize->fserrors[0] == NULL ) {
|
|
alloc_fs_workspace( cinfo );
|
|
}
|
|
/* Initialize the propagated errors to zero. */
|
|
arraysize = (size_t) ( ( cinfo->output_width + 2 ) * SIZEOF( FSERROR ) );
|
|
for ( i = 0; i < cinfo->out_color_components; i++ ) {
|
|
jzero_far( (void FAR *) cquantize->fserrors[i], arraysize );
|
|
}
|
|
break;
|
|
default:
|
|
ERREXIT( cinfo, JERR_NOT_COMPILED );
|
|
break;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Finish up at the end of the pass.
|
|
*/
|
|
|
|
METHODDEF void
|
|
finish_pass_1_quant( j_decompress_ptr cinfo ) {
|
|
/* no work in 1-pass case */
|
|
}
|
|
|
|
|
|
/*
|
|
* Switch to a new external colormap between output passes.
|
|
* Shouldn't get to this module!
|
|
*/
|
|
|
|
METHODDEF void
|
|
new_color_map_1_quant( j_decompress_ptr cinfo ) {
|
|
ERREXIT( cinfo, JERR_MODE_CHANGE );
|
|
}
|
|
|
|
|
|
/*
|
|
* Module initialization routine for 1-pass color quantization.
|
|
*/
|
|
|
|
GLOBAL void
|
|
jinit_1pass_quantizer( j_decompress_ptr cinfo ) {
|
|
my_cquantize_ptr cquantize;
|
|
|
|
cquantize = (my_cquantize_ptr)
|
|
( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
|
|
SIZEOF( my_cquantizer ) );
|
|
cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
|
|
cquantize->pub.start_pass = start_pass_1_quant;
|
|
cquantize->pub.finish_pass = finish_pass_1_quant;
|
|
cquantize->pub.new_color_map = new_color_map_1_quant;
|
|
cquantize->fserrors[0] = NULL;/* Flag FS workspace not allocated */
|
|
cquantize->odither[0] = NULL;/* Also flag odither arrays not allocated */
|
|
|
|
/* Make sure my internal arrays won't overflow */
|
|
if ( cinfo->out_color_components > MAX_Q_COMPS ) {
|
|
ERREXIT1( cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS );
|
|
}
|
|
/* Make sure colormap indexes can be represented by JSAMPLEs */
|
|
if ( cinfo->desired_number_of_colors > ( MAXJSAMPLE + 1 ) ) {
|
|
ERREXIT1( cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE + 1 );
|
|
}
|
|
|
|
/* Create the colormap and color index table. */
|
|
create_colormap( cinfo );
|
|
create_colorindex( cinfo );
|
|
|
|
/* Allocate Floyd-Steinberg workspace now if requested.
|
|
* We do this now since it is FAR storage and may affect the memory
|
|
* manager's space calculations. If the user changes to FS dither
|
|
* mode in a later pass, we will allocate the space then, and will
|
|
* possibly overrun the max_memory_to_use setting.
|
|
*/
|
|
if ( cinfo->dither_mode == JDITHER_FS ) {
|
|
alloc_fs_workspace( cinfo );
|
|
}
|
|
}
|
|
|
|
#endif /* QUANT_1PASS_SUPPORTED */
|