Skip to content
Permalink
Browse files
Fixed bug 3350 - GL renderers don't need to flip rows after reading b…
…ack pixels from the target texture

Simon Hug

All OpenGL renderers always flip the rows of the pixels that come from glReadPixels. This is unnecessary for target textures since these are already top down.

Also, the rect->y value can be used directly for target textures for the same reason. I don't see any code that would handle the logical render size for target textures. Or am I missing something?

The attached patch makes the renderers only the flip rows if the data comes from the default framebuffer.
  • Loading branch information
slouken committed Oct 1, 2016
1 parent 9fff05f commit 51d6371ec1021eeb7ee9851c6d224212f079339b
Showing 3 changed files with 54 additions and 48 deletions.
@@ -1439,28 +1439,30 @@ GL_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,
data->glPixelStorei(GL_PACK_ROW_LENGTH,
(temp_pitch / SDL_BYTESPERPIXEL(temp_format)));

data->glReadPixels(rect->x, (h-rect->y)-rect->h, rect->w, rect->h,
format, type, temp_pixels);
data->glReadPixels(rect->x, renderer->target ? rect->y : (h-rect->y)-rect->h,
rect->w, rect->h, format, type, temp_pixels);

if (GL_CheckError("glReadPixels()", renderer) < 0) {
SDL_free(temp_pixels);
return -1;
}

/* Flip the rows to be top-down */
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
}
SDL_stack_free(tmp);
/* Flip the rows to be top-down if necessary */
if (!renderer->target) {
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
}
SDL_stack_free(tmp);
}

status = SDL_ConvertPixels(rect->w, rect->h,
temp_format, temp_pixels, temp_pitch,
@@ -1088,23 +1088,25 @@ GLES_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,

data->glPixelStorei(GL_PACK_ALIGNMENT, 1);

data->glReadPixels(rect->x, (h-rect->y)-rect->h, rect->w, rect->h,
GL_RGBA, GL_UNSIGNED_BYTE, temp_pixels);

/* Flip the rows to be top-down */
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
data->glReadPixels(rect->x, renderer->target ? rect->y : (h-rect->y)-rect->h,
rect->w, rect->h, GL_RGBA, GL_UNSIGNED_BYTE, temp_pixels);

/* Flip the rows to be top-down if necessary */
if (!renderer->target) {
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
}
SDL_stack_free(tmp);
}
SDL_stack_free(tmp);

status = SDL_ConvertPixels(rect->w, rect->h,
temp_format, temp_pixels, temp_pitch,
@@ -1834,26 +1834,28 @@ GLES2_RenderReadPixels(SDL_Renderer * renderer, const SDL_Rect * rect,

SDL_GetRendererOutputSize(renderer, &w, &h);

data->glReadPixels(rect->x, (h-rect->y)-rect->h, rect->w, rect->h,
GL_RGBA, GL_UNSIGNED_BYTE, temp_pixels);
data->glReadPixels(rect->x, renderer->target ? rect->y : (h-rect->y)-rect->h,
rect->w, rect->h, GL_RGBA, GL_UNSIGNED_BYTE, temp_pixels);
if (GL_CheckError("glReadPixels()", renderer) < 0) {
return -1;
}

/* Flip the rows to be top-down */
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
}
SDL_stack_free(tmp);
/* Flip the rows to be top-down if necessary */
if (!renderer->target) {
length = rect->w * SDL_BYTESPERPIXEL(temp_format);
src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;
dst = (Uint8*)temp_pixels;
tmp = SDL_stack_alloc(Uint8, length);
rows = rect->h / 2;
while (rows--) {
SDL_memcpy(tmp, dst, length);
SDL_memcpy(dst, src, length);
SDL_memcpy(src, tmp, length);
dst += temp_pitch;
src -= temp_pitch;
}
SDL_stack_free(tmp);
}

status = SDL_ConvertPixels(rect->w, rect->h,
temp_format, temp_pixels, temp_pitch,

0 comments on commit 51d6371

Please sign in to comment.