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Fixed bug 4903 - Lack of color multiply with alpha (SDL_BLENDMODE_MOD + SDL_BLENDMODE_BLEND) blending mode for all renderers

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Konrad

This kind of blending is rather quite useful and in my opinion should be available for all renderers. I do need it myself, but since I didn't want to use a custom blending mode which is supported only by certain renderers (e.g. not in software which is quite important for me) I did write implementation of SDL_BLENDMODE_MUL for all renderers altogether.

SDL_BLENDMODE_MUL implements following equation:

dstRGB = (srcRGB * dstRGB) + (dstRGB * (1-srcA))
dstA = (srcA * dstA) + (dstA * (1-srcA))

Background:

https://i.imgur.com/UsYhydP.png

Blended texture:

https://i.imgur.com/0juXQcV.png

Result for SDL_BLENDMODE_MOD:

https://i.imgur.com/wgNSgUl.png

Result for SDL_BLENDMODE_MUL:

https://i.imgur.com/Veokzim.png

I think I did cover all possibilities within included patch, but I didn't write any tests for SDL_BLENDMODE_MUL, so it would be lovely if someone could do it.
This commit is contained in:
Sam Lantinga
2020-01-16 08:52:59 -08:00
parent 669729a8a0
commit 981e0d367c
19 changed files with 819 additions and 159 deletions
Download Patch File Download Diff File Expand all files Collapse all files

56
src/render/software/SDL_draw.h
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@@ -80,6 +80,17 @@ do { \
setpixel; \
} while (0)
#define DRAW_SETPIXEL_MUL(getpixel, setpixel) \
do { \
unsigned sr, sg, sb, sa; sa = 0xFF; \
getpixel; \
sr = DRAW_MUL(sr, r) + DRAW_MUL(inva, sr); if (sr > 0xff) sr = 0xff; \
sg = DRAW_MUL(sg, g) + DRAW_MUL(inva, sg); if (sg > 0xff) sg = 0xff; \
sb = DRAW_MUL(sb, b) + DRAW_MUL(inva, sb); if (sb > 0xff) sb = 0xff; \
sa = DRAW_MUL(sa, a) + DRAW_MUL(inva, sa); if (sa > 0xff) sa = 0xff; \
setpixel; \
} while (0)
#define DRAW_SETPIXELXY(x, y, type, bpp, op) \
do { \
type *pixel = (type *)((Uint8 *)dst->pixels + (y) * dst->pitch \
@@ -106,6 +117,10 @@ do { \
DRAW_SETPIXEL_MOD(RGB_FROM_RGB555(*pixel, sr, sg, sb), \
RGB555_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXEL_MUL_RGB555 \
DRAW_SETPIXEL_MUL(RGB_FROM_RGB555(*pixel, sr, sg, sb), \
RGB555_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXELXY_RGB555(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_RGB555)
@@ -118,6 +133,9 @@ do { \
#define DRAW_SETPIXELXY_MOD_RGB555(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_MOD_RGB555)
#define DRAW_SETPIXELXY_MUL_RGB555(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_MUL_RGB555)
/*
* Define draw operators for RGB565
*/
@@ -137,6 +155,10 @@ do { \
DRAW_SETPIXEL_MOD(RGB_FROM_RGB565(*pixel, sr, sg, sb), \
RGB565_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXEL_MUL_RGB565 \
DRAW_SETPIXEL_MUL(RGB_FROM_RGB565(*pixel, sr, sg, sb), \
RGB565_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXELXY_RGB565(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_RGB565)
@@ -149,6 +171,9 @@ do { \
#define DRAW_SETPIXELXY_MOD_RGB565(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_MOD_RGB565)
#define DRAW_SETPIXELXY_MUL_RGB565(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_MUL_RGB565)
/*
* Define draw operators for RGB888
*/
@@ -168,6 +193,10 @@ do { \
DRAW_SETPIXEL_MOD(RGB_FROM_RGB888(*pixel, sr, sg, sb), \
RGB888_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXEL_MUL_RGB888 \
DRAW_SETPIXEL_MUL(RGB_FROM_RGB888(*pixel, sr, sg, sb), \
RGB888_FROM_RGB(*pixel, sr, sg, sb))
#define DRAW_SETPIXELXY_RGB888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_RGB888)
@@ -180,6 +209,9 @@ do { \
#define DRAW_SETPIXELXY_MOD_RGB888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MOD_RGB888)
#define DRAW_SETPIXELXY_MUL_RGB888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MUL_RGB888)
/*
* Define draw operators for ARGB8888
*/
@@ -199,6 +231,10 @@ do { \
DRAW_SETPIXEL_MOD(RGBA_FROM_ARGB8888(*pixel, sr, sg, sb, sa), \
ARGB8888_FROM_RGBA(*pixel, sr, sg, sb, sa))
#define DRAW_SETPIXEL_MUL_ARGB8888 \
DRAW_SETPIXEL_MUL(RGBA_FROM_ARGB8888(*pixel, sr, sg, sb, sa), \
ARGB8888_FROM_RGBA(*pixel, sr, sg, sb, sa))
#define DRAW_SETPIXELXY_ARGB8888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_ARGB8888)
@@ -211,6 +247,9 @@ do { \
#define DRAW_SETPIXELXY_MOD_ARGB8888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MOD_ARGB8888)
#define DRAW_SETPIXELXY_MUL_ARGB8888(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MUL_ARGB8888)
/*
* Define draw operators for general RGB
*/
@@ -230,6 +269,10 @@ do { \
DRAW_SETPIXEL_MOD(RGB_FROM_PIXEL(*pixel, fmt, sr, sg, sb), \
PIXEL_FROM_RGB(*pixel, fmt, sr, sg, sb))
#define DRAW_SETPIXEL_MUL_RGB \
DRAW_SETPIXEL_MUL(RGB_FROM_PIXEL(*pixel, fmt, sr, sg, sb), \
PIXEL_FROM_RGB(*pixel, fmt, sr, sg, sb))
#define DRAW_SETPIXELXY2_RGB(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_RGB)
@@ -254,6 +297,12 @@ do { \
#define DRAW_SETPIXELXY4_MOD_RGB(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MOD_RGB)
#define DRAW_SETPIXELXY2_MUL_RGB(x, y) \
DRAW_SETPIXELXY(x, y, Uint16, 2, DRAW_SETPIXEL_MUL_RGB)
#define DRAW_SETPIXELXY4_MUL_RGB(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MUL_RGB)
/*
* Define draw operators for general RGBA
@@ -274,6 +323,10 @@ do { \
DRAW_SETPIXEL_MOD(RGBA_FROM_PIXEL(*pixel, fmt, sr, sg, sb, sa), \
PIXEL_FROM_RGBA(*pixel, fmt, sr, sg, sb, sa))
#define DRAW_SETPIXEL_MUL_RGBA \
DRAW_SETPIXEL_MUL(RGBA_FROM_PIXEL(*pixel, fmt, sr, sg, sb, sa), \
PIXEL_FROM_RGBA(*pixel, fmt, sr, sg, sb, sa))
#define DRAW_SETPIXELXY4_RGBA(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_RGBA)
@@ -286,6 +339,9 @@ do { \
#define DRAW_SETPIXELXY4_MOD_RGBA(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MOD_RGBA)
#define DRAW_SETPIXELXY4_MUL_RGBA(x, y) \
DRAW_SETPIXELXY(x, y, Uint32, 4, DRAW_SETPIXEL_MUL_RGBA)
/*
* Define line drawing macro
*/