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Introduce gdLayerDiff() and gdEffectDiff #920

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Introduce gdLayerDiff() and gdEffectDiff #920

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ad9d75e
Introduce gdLayerDiff() and gdEffectDiff
cmb69 Jan 1, 2025
0f0b48f
remove unused variable
cmb69 Jan 1, 2025
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45 changes: 45 additions & 0 deletions src/gd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1299,6 +1299,9 @@ BGD_DECLARE(void) gdImageSetPixel (gdImagePtr im, int x, int y, int color)
case gdEffectMultiply :
im->tpixels[y][x] = gdLayerMultiply(im->tpixels[y][x], color);
break;
case gdEffectDiff :
im->tpixels[y][x] = gdLayerDiff(im->tpixels[y][x], color);
break;
}
} else {
im->pixels[y][x] = color;
Expand Down Expand Up @@ -4070,6 +4073,7 @@ BGD_DECLARE(int) gdImageCompare (gdImagePtr im1, gdImagePtr im2)
* - <gdImageAlphaBlending>
* - <gdLayerOverlay>
* - <gdLayerMultiply>
* - <gdLayerDiff>
*/
BGD_DECLARE(int) gdAlphaBlend (int dst, int src)
{
Expand Down Expand Up @@ -4131,6 +4135,7 @@ static int gdAlphaOverlayColor (int src, int dst, int max );
* - <gdImageAlphaBlending>
* - <gdAlphaBlend>
* - <gdLayerMultiply>
* - <gdLayerDiff>
*/
BGD_DECLARE(int) gdLayerOverlay (int dst, int src)
{
Expand Down Expand Up @@ -4170,6 +4175,7 @@ static int gdAlphaOverlayColor (int src, int dst, int max )
* - <gdImageAlphaBlending>
* - <gdAlphaBlend>
* - <gdLayerOverlay>
* - <gdLayerDiff>
*/
BGD_DECLARE(int) gdLayerMultiply (int dst, int src)
{
Expand All @@ -4193,6 +4199,45 @@ BGD_DECLARE(int) gdLayerMultiply (int dst, int src)
);
}

/**
* Function: gdLayerDiff
*
* Difference of two colors; commutative operation.
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should it note that it's absolute ?

*
* Parameters:
* dst - The first color.
* src - The second color.
*
* See also:
* - <gdImageAlphaBlending>
* - <gdAlphaBlend>
* - <gdLayerMultiply>
* - <gdLayerOverlay>
*/
BGD_DECLARE(int) gdLayerDiff (int dst, int src)
{
int r1,b1,g1,a1,r2,b2,g2,a2;
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spaces after commas please

int diff_a,diff_r,diff_g,diff_b;

a1 = gdTrueColorGetAlpha(dst);
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i'm on the fence whether all these variables are needed vs a single statement.

    return gdTrueColorAlpha(
        abs(gdTrueColorGetAlpha(dst) - gdTrueColorGetAlpha(src)),
        abs(gdTrueColorGetRed(dst) - gdTrueColorGetRed(src)),
        abs(gdTrueColorGetGreen(dst) - gdTrueColorGetGreen(src)),
        abs(gdTrueColorGetBlue(dst) - gdTrueColorGetBlue(src)));

a2 = gdTrueColorGetAlpha(src);
diff_a = abs(a1 - a2);

r1 = gdTrueColorGetRed(dst);
r2 = gdTrueColorGetRed(src);
diff_r = abs(r1 - r2);

g1 = gdTrueColorGetGreen(dst);
g2 = gdTrueColorGetGreen(src);
diff_g = abs(g1 - g2);

b1 = gdTrueColorGetBlue(dst);
b2 = gdTrueColorGetBlue(src);
diff_b = abs(b1 - b2);

return gdTrueColorAlpha(diff_r, diff_g, diff_b, diff_a);
}

/**
* Function: gdImageAlphaBlending
*
Expand Down
4 changes: 4 additions & 0 deletions src/gd.h
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Expand Up @@ -220,6 +220,8 @@ extern "C" {
* gdEffectOverlay - overlay pixels, see <gdLayerOverlay>
* gdEffectMultiply - overlay pixels with multiply effect, see
* <gdLayerMultiply>
* gdEffectDiff - replace pixels with their difference, see
* <gdLayerDiff>
*
* See also:
* - <gdImageAlphaBlending>
Expand All @@ -229,6 +231,7 @@ extern "C" {
#define gdEffectNormal 2
#define gdEffectOverlay 3
#define gdEffectMultiply 4
#define gdEffectDiff 5

#define GD_TRUE 1
#define GD_FALSE 0
Expand All @@ -246,6 +249,7 @@ extern "C" {
BGD_DECLARE(int) gdAlphaBlend (int dest, int src);
BGD_DECLARE(int) gdLayerOverlay (int dest, int src);
BGD_DECLARE(int) gdLayerMultiply (int dest, int src);
BGD_DECLARE(int) gdLayerDiff (int dest, int src);


/**
Expand Down
1 change: 1 addition & 0 deletions tests/gdimagesetpixel/CMakeLists.txt
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Expand Up @@ -2,6 +2,7 @@ LIST(APPEND TESTS_FILES
bug00186
gdeffectoverlay
gdeffectmultiply
gdeffectdiff
)

IF(PNG_FOUND)
Expand Down
3 changes: 2 additions & 1 deletion tests/gdimagesetpixel/Makemodule.am
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@@ -1,7 +1,8 @@
libgd_test_programs += \
gdimagesetpixel/bug00186 \
gdimagesetpixel/gdeffectmultiply \
gdimagesetpixel/gdeffectoverlay
gdimagesetpixel/gdeffectoverlay \
gdimagesetpixel/gdeffectdiff

if HAVE_LIBPNG
libgd_test_programs += \
Expand Down
33 changes: 33 additions & 0 deletions tests/gdimagesetpixel/gdeffectdiff.c
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@@ -0,0 +1,33 @@
#include "gd.h"
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please add a proper file header: license, copyright, and text explaining the test goals.

#include "gdtest.h"

int main()
{
gdImagePtr im;
int x, y, c;
int r=0;
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spaces around binary operators like =



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only one blank line

im = gdImageCreateTrueColor(256, 256);
gdImageAlphaBlending( im, gdEffectReplace );
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no space after ( or before )

for (x=0; x<256; x++) {
for (y=0; y<256; y++) {
c = (y/2 << 24) + (x << 16) + (x << 8) + x;
gdImageSetPixel(im, x, y, c );
}
}
gdImageAlphaBlending( im, gdEffectDiff );
gdImageFilledRectangle(im, 0, 0, 255, 255, 0xff7f00);

if (gdTrueColorGetGreen(gdImageGetPixel(im, 0, 128)) != 0x7f) {
r = 1;
}
if (gdTrueColorGetGreen(gdImageGetPixel(im, 128, 128)) != 0x01) {
r = 1;
}
if (gdTrueColorGetGreen(gdImageGetPixel(im, 255, 128)) != 0x80) {
r = 1;
}
gdImageDestroy(im);
return r;
}
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