pandory500/SDL-mirror
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Updated blend semantics so blending uses the following formula:

Browse source 
dstRGB = (srcRGB * srcA) + (dstRGB * (1-srcA))
    dstA = srcA + (dstA * (1-srcA))
This allows proper compositing semantics without requiring premultiplied alpha.

Needs full unit test coverage and bug fixes!
This commit is contained in:
Sam Lantinga 2013-07-23 08:06:49 -07:00
parent a99edf3519
commit 32188834b5
17 changed files with 362 additions and 1001 deletions
Download patch file Download diff file Expand all files Collapse all files

108
test/testrendertarget.c
View file

@ -87,6 +87,88 @@ LoadTexture(SDL_Renderer *renderer, char *file, SDL_bool transparent)
return texture;
}
void
DrawComposite(DrawState *s)
{
SDL_Rect viewport, R;
SDL_Texture *target, *A, *B;
static SDL_bool blend_tested = SDL_FALSE;
if (!blend_tested) {
SDL_Texture *A, *B;
Uint32 P;
A = SDL_CreateTexture(s->renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, 1, 1);
SDL_SetTextureBlendMode(A, SDL_BLENDMODE_BLEND);
B = SDL_CreateTexture(s->renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, 1, 1);
SDL_SetTextureBlendMode(B, SDL_BLENDMODE_BLEND);
SDL_SetRenderTarget(s->renderer, A);
SDL_SetRenderDrawColor(s->renderer, 0x00, 0x00, 0x00, 0x80);
SDL_RenderFillRect(s->renderer, NULL);
SDL_SetRenderTarget(s->renderer, B);
SDL_SetRenderDrawColor(s->renderer, 0x00, 0x00, 0x00, 0x00);
SDL_RenderFillRect(s->renderer, NULL);
SDL_RenderCopy(s->renderer, A, NULL, NULL);
SDL_RenderReadPixels(s->renderer, NULL, SDL_PIXELFORMAT_ARGB8888, &P, sizeof(P));
printf("Blended pixel: 0x%8.8X\n", P);
SDL_DestroyTexture(A);
SDL_DestroyTexture(B);
blend_tested = SDL_TRUE;
}
SDL_RenderGetViewport(s->renderer, &viewport);
target = SDL_CreateTexture(s->renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_TARGET, viewport.w, viewport.h);
SDL_SetTextureBlendMode(target, SDL_BLENDMODE_BLEND);
SDL_SetRenderTarget(s->renderer, target);
/* Draw the background.
This is solid black so when the sprite is copied to it, any per-pixel alpha will be blended through.
*/
SDL_SetRenderDrawColor(s->renderer, 0x00, 0x00, 0x00, 0x00);
SDL_RenderFillRect(s->renderer, NULL);
/* Scale and draw the sprite */
s->sprite_rect.w += s->scale_direction;
s->sprite_rect.h += s->scale_direction;
if (s->scale_direction > 0) {
if (s->sprite_rect.w >= viewport.w || s->sprite_rect.h >= viewport.h) {
s->scale_direction = -1;
}
} else {
if (s->sprite_rect.w <= 1 || s->sprite_rect.h <= 1) {
s->scale_direction = 1;
}
}
s->sprite_rect.x = (viewport.w - s->sprite_rect.w) / 2;
s->sprite_rect.y = (viewport.h - s->sprite_rect.h) / 2;
SDL_RenderCopy(s->renderer, s->sprite, NULL, &s->sprite_rect);
SDL_SetRenderTarget(s->renderer, NULL);
SDL_RenderCopy(s->renderer, s->background, NULL, NULL);
SDL_SetRenderDrawBlendMode(s->renderer, SDL_BLENDMODE_BLEND);
SDL_SetRenderDrawColor(s->renderer, 0xff, 0x00, 0x00, 0x80);
R.x = 0;
R.y = 0;
R.w = 100;
R.h = 100;
SDL_RenderFillRect(s->renderer, &R);
SDL_SetRenderDrawBlendMode(s->renderer, SDL_BLENDMODE_NONE);
SDL_RenderCopy(s->renderer, target, NULL, NULL);
SDL_DestroyTexture(target);
/* Update the screen! */
SDL_RenderPresent(s->renderer);
}
void
Draw(DrawState *s)
{
@ -134,6 +216,7 @@ main(int argc, char *argv[])
SDL_Event event;
int frames;
Uint32 then, now;
SDL_bool test_composite = SDL_FALSE;
/* Initialize test framework */
state = SDLTest_CommonCreateState(argv, SDL_INIT_VIDEO);
@ -145,8 +228,17 @@ main(int argc, char *argv[])
consumed = SDLTest_CommonArg(state, i);
if (consumed == 0) {
fprintf(stderr, "Usage: %s %s\n", argv[0], SDLTest_CommonUsage(state));
return 1;
consumed = -1;
if (SDL_strcasecmp(argv[i], "--composite") == 0) {
test_composite = SDL_TRUE;
consumed = 1;
}
}
if (consumed < 0) {
fprintf(stderr,
"Usage: %s %s [--composite]\n",
argv[0], SDLTest_CommonUsage(state));
quit(1);
}
i += consumed;
}
@ -160,7 +252,11 @@ main(int argc, char *argv[])
drawstate->window = state->windows[i];
drawstate->renderer = state->renderers[i];
drawstate->sprite = LoadTexture(drawstate->renderer, "icon.bmp", SDL_TRUE);
if (test_composite) {
drawstate->sprite = LoadTexture(drawstate->renderer, "icon-alpha.bmp", SDL_TRUE);
} else {
drawstate->sprite = LoadTexture(drawstate->renderer, "icon.bmp", SDL_TRUE);
}
drawstate->background = LoadTexture(drawstate->renderer, "sample.bmp", SDL_FALSE);
if (!drawstate->sprite || !drawstate->background) {
quit(2);
@ -181,7 +277,11 @@ main(int argc, char *argv[])
SDLTest_CommonEvent(state, &event, &done);
}
for (i = 0; i < state->num_windows; ++i) {
Draw(&drawstates[i]);
if (test_composite) {
DrawComposite(&drawstates[i]);
} else {
Draw(&drawstates[i]);
}
}
}