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Implemented binary search for colors in HLSL

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This commit is contained in:
Robert Beckebans 2023-12-27 15:14:58 +01:00
parent 9e88365c59
commit a589f3e6f0
1 changed files with 69 additions and 13 deletions
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82
neo/shaders/builtin/post/retro_c64.ps.hlsl
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@ -50,22 +50,12 @@ struct PS_OUT
// *INDENT-ON*
float3 BlueNoise3( float2 n, float x )
{
float2 uv = n.xy * rpJitterTexOffset.xy;
float3 noise = t_BlueNoise.Sample( samp1, uv ).rgb;
noise = frac( noise + c_goldenRatioConjugate * rpJitterTexOffset.w * x );
return noise;
}
#define RESOLUTION_DIVISOR 4.0
#define NUM_COLORS 16
// find nearest palette color using Euclidean distance
float4 EuclidDist( float3 c, float3 pal[NUM_COLORS] )
float4 LinearSearch( float3 c, float3 pal[NUM_COLORS] )
{
int idx = 0;
float nd = distance( c, pal[0] );
@ -84,6 +74,71 @@ float4 EuclidDist( float3 c, float3 pal[NUM_COLORS] )
return float4( pal[idx], 1.0 );
}
float3 GetClosest( float3 val1, float3 val2, float3 target )
{
if( distance( target, val1 ) >= distance( val2, target ) )
{
return val2;
}
else
{
return val1;
}
}
// find nearest palette color using Euclidean disntance and binary search
// this requires an already sorted palette as input
float3 BinarySearch( float3 target, float3 pal[NUM_COLORS] )
{
float targetY = PhotoLuma( target );
// left-side case
if( targetY <= PhotoLuma( pal[0] ) )
{
return pal[0];
}
// right-side case
if( targetY >= PhotoLuma( pal[NUM_COLORS - 1] ) )
{
return pal[NUM_COLORS - 1];
}
int i = 0, j = NUM_COLORS, mid = 0;
while( i < j )
{
mid = ( i + j ) / 2;
if( distance( pal[mid], target ) < 0.01 )
{
return pal[mid];
}
// if target is less than array element, then search in left
if( targetY < PhotoLuma( pal[mid] ) )
{
// if target is greater than previous
// to mid, return closest of two
if( mid > 0 && targetY > PhotoLuma( pal[mid - 1] ) )
{
return GetClosest( pal[mid - 1], pal[mid], target );
}
j = mid;
}
else
{
if( mid < ( NUM_COLORS - 1 ) && targetY < PhotoLuma( pal[mid + 1] ) )
{
return GetClosest( pal[mid], pal[mid + 1], target );
}
i = mid + 1;
}
}
// only single element left after search
return pal[mid];
}
#define RGB(r, g, b) float3(float(r)/255.0, float(g)/255.0, float(b)/255.0)
@ -151,7 +206,8 @@ void main( PS_IN fragment, out PS_OUT result )
#endif
// find closest color match from C64 color palette
color = EuclidDist( color.rgb, palette );
color = LinearSearch( color.rgb, palette );
//color = float4( BinarySearch( color.rgb, palette ), 1.0 );
result.color = color;
}