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cleanup

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This commit is contained in:
Glenn Maynard
2004-09-04 04:30:36 +00:00
parent fdbe1b01dd
commit a6d3516b69
1 changed files with 36 additions and 71 deletions
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stepmania/src/SDL_dither.cpp
+36 -71
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@@ -38,8 +38,8 @@ static uint8_t DitherPixel(int x, int y, int intensity, int conv)
* bits directly gives 6.25. A matrix value of 0 means the pixel is not * bits directly gives 6.25. A matrix value of 0 means the pixel is not
* biased at all, which would cause it to be truncated to 6. A value * biased at all, which would cause it to be truncated to 6. A value
* of 5/16 means that the value is biased to 6.5625, which is also truncated * of 5/16 means that the value is biased to 6.5625, which is also truncated
* to 6. A value of 15/16 biases to 6.1875, which causes it to be rounded * to 6. A value of 15/16 biases to 7.1875, which causes it to be rounded
* up to 6. So, a proportion of pixels gets rounded up based on how close * up to 7. So, a proportion of pixels gets rounded up based on how close
* the number is to the next value. */ * the number is to the next value. */
/* Convert the number to the destination range. */ /* Convert the number to the destination range. */
@@ -97,8 +97,8 @@ void RageSurfaceUtils::OrderedDither( const RageSurface *src, RageSurface *dst )
/* For each row: */ /* For each row: */
for( int row = 0; row < src->h; ++row ) for( int row = 0; row < src->h; ++row )
{ {
const uint8_t *srcp = (const uint8_t *) src->pixels + row * src->pitch; const uint8_t *srcp = src->pixels + row * src->pitch;
uint8_t *dstp = (uint8_t *) dst->pixels + row * dst->pitch; uint8_t *dstp = dst->pixels + row * dst->pitch;
/* For each pixel: */ /* For each pixel: */
for( int col = 0; col < src->w; ++col ) for( int col = 0; col < src->w; ++col )
@@ -124,13 +124,7 @@ void RageSurfaceUtils::OrderedDither( const RageSurface *src, RageSurface *dst )
* looks bad on the alpha channel. */ * looks bad on the alpha channel. */
int out_intensity = colors[3] * conv[3]; int out_intensity = colors[3] * conv[3];
/* Truncate, and add e to make sure a value of 14.999998 -> 15. */ /* Round: */
// colors[3] = uint8_t((out_intensity + 1) >> 16);
/* I don't remember why this used to truncate. Doing that causes
* dithering to an image with 1-bit alpha to be transparent on all
* source alpha values except for full-opaque, which is wrong.
* Add .5, so we round. */
colors[3] = uint8_t((out_intensity + 32767) >> 16); colors[3] = uint8_t((out_intensity + 32767) >> 16);
} }
@@ -144,25 +138,34 @@ void RageSurfaceUtils::OrderedDither( const RageSurface *src, RageSurface *dst )
} }
/* Return "random" numbers in [0,2]; this is for SM_SDL_ErrorDiffusionDither (rand() is too slow). */ static uint8_t EDDitherPixel( int x, int y, int intensity, int conv, int32_t &accumError )
/* static inline int GetFastRand()
{ {
static int RandomNumbers[] = /* Convert the number to the destination range. */
{ int out_intensity = intensity * conv;
2, 1, 0, 2, 0, 2, 2, 1, 0, 1, 1, 2, 2, 0, 1, 1, 2, 2, 1, 0, 1, 0, 1, 2, 1, 0, 2, 1, 0, 1, 1, 0,
2, 1, 1, 2, 1, 0, 0, 1, 1, 2, 0, 2, 0, 1, 0, 1, 2, 0, 0, 1, 1, 2, 0, 2, 1, 2, 2, 2, 2, 1, 1, 1, /* Add e to make sure a value of 14.999998 -> 15. */
1, 0, 2, 1, 2, 1, 1, 1, 2, 1, 0, 0, 1, 0, 0, 2, 0, 1, 0, 1, 2, 2, 0, 0, 0, 2, 2, 1, 2, 2, 2, 2, ++out_intensity;
1, 2, 1, 0, 2, 0, 1, 0, 2, 1, 2, 1, 1, 0, 1, 1, 2, 0, 0, 2, 2, 2, 1, 0, 0, 1, 2, 1, 2, 0, 0, 2,
2, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 2, 2, 2, 0, 0, 0, 1, 2, 0, 1, 1, 0, 0, 0, 2, 1, 2, 0, 0, 1, /* Add bias. */
1, 2, 0, 1, 1, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 0, 0, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 2, out_intensity += accumError;
0, 1, 2, 0, 2, 2, 0, 2, 1, 0, 0, 2, 2, 2, 2, 2, 2, 1, 1, 2, 2, 2, 0, 1, 0, 1, 2, 1, 2, 1, 0, 0,
1, 0, 0, 0, 2, 2, 2, 2, 1, 2, 1, 0, 0, 2, 1, 0, 1, 2, 0, 2, 2, 0, 0, 0, 2, 2, 0, 0, 2, 0, 1, 1 /* out_intensity is now what we actually want this component to be.
}; * To store it, we have to clamp it (prevent overflow) and shift it
static int iNextNumber = 0; * from fixed-point to [0,255]. The error introduced in that calculation
if( iNextNumber == ARRAYSIZE(RandomNumbers) ) * becomes the new accumError. */
iNextNumber = 0; int clamped_intensity = clamp( out_intensity, 0, 0xFFFFFF );
return RandomNumbers[ iNextNumber++ ]; clamped_intensity &= 0xFF0000;
} */
/* Truncate. */
uint8_t ret = uint8_t(clamped_intensity >> 16);
accumError = out_intensity - clamped_intensity;
// Reduce funky streaks in low-bit channels by clamping error.
CLAMP( accumError, -128 * 65536, +128 * 65536 );
return ret;
}
/* This is very similar to SM_SDL_OrderedDither, except instead of using a matrix /* This is very similar to SM_SDL_OrderedDither, except instead of using a matrix
* containing rounding values, we truncate and then add the resulting error for * containing rounding values, we truncate and then add the resulting error for
@@ -197,8 +200,8 @@ void RageSurfaceUtils::ErrorDiffusionDither( const RageSurface *src, RageSurface
{ {
int32_t accumError[4] = { 0, 0, 0, 0 }; // accum error values are reset every row int32_t accumError[4] = { 0, 0, 0, 0 }; // accum error values are reset every row
const uint8_t *srcp = (const uint8_t *)src->pixels + row * src->pitch; const uint8_t *srcp = src->pixels + row * src->pitch;
uint8_t *dstp = (uint8_t *)dst->pixels + row * dst->pitch; uint8_t *dstp = dst->pixels + row * dst->pitch;
/* For each pixel in row: */ /* For each pixel in row: */
for( int col = 0; col < src->w; ++col ) for( int col = 0; col < src->w; ++col )
@@ -208,39 +211,7 @@ void RageSurfaceUtils::ErrorDiffusionDither( const RageSurface *src, RageSurface
for( int c = 0; c < 3; ++c ) for( int c = 0; c < 3; ++c )
{ {
/* Convert the number to the destination range. */ colors[c] = EDDitherPixel( col, row, colors[c], conv[c], accumError[c] );
int out_intensity = colors[c] * conv[c];
/* Add e to make sure a value of 14.999998 -> 15. */
++out_intensity;
/* Add bias. */
out_intensity += accumError[c];
/* out_intensity is now what we actually want this component to be.
* To store it, we have to clamp it (prevent overflow) and shift it
* from fixed-point to [0,255]. The error introduced in that calculation
* becomes the new accumError. */
int clamped_intensity = clamp( out_intensity, 0, 0xFFFFFF );
clamped_intensity &= 0xFF0000;
/* Truncate. */
colors[c] = uint8_t(clamped_intensity >> 16);
accumError[c] = out_intensity - clamped_intensity;
// Reduce funky streaks in low-bit channels by clamping error.
CLAMP( accumError[c], -128 * 65536, +128 * 65536 );
// Keep only a fraction of the error to make the effect more subtle.
// This used to divide by [1,4]; shift right by [0,2] to get a similar
// (but much faster) effect.
/* This resulted in banding in gradients, and doesn't work quite the
* same way with this calculation; without it, gradients look correct.
* Unfortunately, I don't remember any of the problem cases we had
* originally; if we see problems with the dithering in the future, let's
* archive them somewhere for future testing. */
// accumError[c] >>= (GetFastRand())+1;
} }
/* If the source has no alpha, the conversion formula will end up /* If the source has no alpha, the conversion formula will end up
@@ -254,13 +225,7 @@ void RageSurfaceUtils::ErrorDiffusionDither( const RageSurface *src, RageSurface
* looks bad on the alpha channel. */ * looks bad on the alpha channel. */
int out_intensity = colors[3] * conv[3]; int out_intensity = colors[3] * conv[3];
/* Truncate, and add e to make sure a value of 14.999998 -> 15. */ /* Round: */
// colors[3] = uint8_t((out_intensity + 1) >> 16);
/* I don't remember why this used to truncate. Doing that causes
* dithering to an image with 1-bit alpha to be transparent on all
* source alpha values except for full-opaque, which is wrong.
* Add .5, so we round. */
colors[3] = uint8_t((out_intensity + 32767) >> 16); colors[3] = uint8_t((out_intensity + 32767) >> 16);
} }