Contrast support with a "contrast" cvar, behaving the same as MarkV's.

It may be a useful alternative to the existing gamma control for laptops in a bright environment, etc.
(raising contrast gives less of a gray/washed out look than raising gamma, but as a disadvantage, colours near white get clipped to white.)

It's also implemented for both GLSL and SDL gamma ramps, but only if USE_GAMMA_RAMPS is set to 1.
Since USE_GAMMA_RAMPS  is 0, currently it only works with GLSL.

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@1290 af15c1b1-3010-417e-b628-4374ebc0bcbd

Quake/gl_rmain.c

@@ -124,6 +124,7 @@ static int r_gamma_texture_width, r_gamma_texture_height;
 
 // uniforms used in gamma shader
 static GLuint gammaLoc;
+static GLuint contrastLoc;
 static GLuint textureLoc;
 
 /*
@@ -158,9 +159,11 @@ static void GLSLGamma_CreateShaders (void)
 		"\n"
 		"uniform sampler2D GammaTexture;\n"
 		"uniform float GammaValue;\n"
+		"uniform float ContrastValue;\n"
 		"\n"
 		"void main(void) {\n"
 		"	  vec4 frag = texture2D(GammaTexture, gl_TexCoord[0].xy);\n"
+		"	  frag.rgb = frag.rgb * ContrastValue;\n"
 		"	  gl_FragColor = vec4(pow(frag.rgb, vec3(GammaValue)), 1.0);\n"
 		"}\n";
 
@@ -171,6 +174,7 @@ static void GLSLGamma_CreateShaders (void)
 
 // get uniform locations
 	gammaLoc = GL_GetUniformLocation (&r_gamma_program, "GammaValue");
+	contrastLoc = GL_GetUniformLocation (&r_gamma_program, "ContrastValue");
 	textureLoc = GL_GetUniformLocation (&r_gamma_program, "GammaTexture");
 }
 
@@ -186,7 +190,7 @@ void GLSLGamma_GammaCorrect (void)
 	if (!gl_glsl_gamma_able)
 		return;
 
-	if (vid_gamma.value == 1)
+	if (vid_gamma.value == 1 && vid_contrast.value == 1)
 		return;
 
 // create render-to-texture texture if needed
@@ -227,6 +231,7 @@ void GLSLGamma_GammaCorrect (void)
 // draw the texture back to the framebuffer with a fragment shader
 	GL_UseProgramFunc (r_gamma_program);
 	GL_Uniform1fFunc (gammaLoc, vid_gamma.value);
+	GL_Uniform1fFunc (contrastLoc, q_min(2.0, q_max(1.0, vid_contrast.value)));
 	GL_Uniform1iFunc (textureLoc, 0); // use texture unit 0
 
 	glDisable (GL_ALPHA_TEST);

Quake/gl_vidsdl.c

@@ -152,6 +152,7 @@ static cvar_t	vid_desktopfullscreen = {"vid_desktopfullscreen", "0", CVAR_ARCHIV
 //johnfitz
 
 cvar_t		vid_gamma = {"gamma", "1", CVAR_ARCHIVE}; //johnfitz -- moved here from view.c
+cvar_t		vid_contrast = {"contrast", "1", CVAR_ARCHIVE}; //QuakeSpasm, MarkV
 
 //==========================================================================
 //
@@ -271,7 +272,7 @@ static void VID_Gamma_f (cvar_t *var)
 	for (i = 0; i < 256; i++)
 	{
 		vid_gamma_red[i] =
-			CLAMP(0, (int) (255 * pow((i + 0.5)/255.5, var->value) + 0.5), 255) << 8;
+			CLAMP(0, (int) ((255 * pow((i + 0.5)/255.5, vid_gamma.value) + 0.5) * vid_contrast.value), 255) << 8;
 		vid_gamma_green[i] = vid_gamma_red[i];
 		vid_gamma_blue[i] = vid_gamma_red[i];
 	}
@@ -287,7 +288,9 @@ VID_Gamma_Init -- call on init
 static void VID_Gamma_Init (void)
 {
 	Cvar_RegisterVariable (&vid_gamma);
+	Cvar_RegisterVariable (&vid_contrast);
 	Cvar_SetCallback (&vid_gamma, VID_Gamma_f);
+	Cvar_SetCallback (&vid_contrast, VID_Gamma_f);
 
 	if (gl_glsl_gamma_able)
 		return;

Quake/menu.c

@@ -965,6 +965,7 @@ enum
 	OPT_SCALE,
 	OPT_SCRSIZE,
 	OPT_GAMMA,
+	OPT_CONTRAST,
 	OPT_MOUSESPEED,
 	OPT_SBALPHA,
 	OPT_SNDVOL,
@@ -1024,6 +1025,12 @@ void M_AdjustSliders (int dir)
 		else if (f > 1)	f = 1;
 		Cvar_SetValue ("gamma", f);
 		break;
+	case OPT_CONTRAST:	// contrast
+		f = vid_contrast.value + dir * 0.1;
+		if (f < 1)	f = 1;
+		else if (f > 2)	f = 2;
+		Cvar_SetValue ("contrast", f);
+		break;
 	case OPT_MOUSESPEED:	// mouse speed
 		f = sensitivity.value + dir * 0.5;
 		if (f > 11)	f = 11;
@@ -1151,6 +1158,11 @@ void M_Options_Draw (void)
 	r = (1.0 - vid_gamma.value) / 0.5;
 	M_DrawSlider (220, 32 + 8*OPT_GAMMA, r);
 
+	// OPT_CONTRAST:
+	M_Print (16, 32 + 8*OPT_CONTRAST,	"              Contrast");
+	r = vid_contrast.value - 1.0;
+	M_DrawSlider (220, 32 + 8*OPT_CONTRAST, r);
+	
 	// OPT_MOUSESPEED:
 	M_Print (16, 32 + 8*OPT_MOUSESPEED,	"           Mouse Speed");
 	r = (sensitivity.value - 1)/10;

Quake/view.h

@@ -24,6 +24,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #define _QUAKE_VIEW_H
 
 extern	cvar_t		vid_gamma;
+extern	cvar_t		vid_contrast;
 
 extern float v_blend[4];