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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 0cb537758c
commit 7328bbad9e
19 changed files with 819 additions and 159 deletions
Download patch file Download diff file Expand all files Collapse all files

21
src/render/software/SDL_blendfillrect.c
View file

@ -42,6 +42,9 @@ SDL_BlendFillRect_RGB555(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB555);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint16, DRAW_SETPIXEL_MUL_RGB555);
break;
default:
FILLRECT(Uint16, DRAW_SETPIXEL_RGB555);
break;
@ -65,6 +68,9 @@ SDL_BlendFillRect_RGB565(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB565);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint16, DRAW_SETPIXEL_MUL_RGB565);
break;
default:
FILLRECT(Uint16, DRAW_SETPIXEL_RGB565);
break;
@ -88,6 +94,9 @@ SDL_BlendFillRect_RGB888(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGB888);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint32, DRAW_SETPIXEL_MUL_RGB888);
break;
default:
FILLRECT(Uint32, DRAW_SETPIXEL_RGB888);
break;
@ -111,6 +120,9 @@ SDL_BlendFillRect_ARGB8888(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint32, DRAW_SETPIXEL_MOD_ARGB8888);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint32, DRAW_SETPIXEL_MUL_ARGB8888);
break;
default:
FILLRECT(Uint32, DRAW_SETPIXEL_ARGB8888);
break;
@ -137,6 +149,9 @@ SDL_BlendFillRect_RGB(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint16, DRAW_SETPIXEL_MOD_RGB);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint16, DRAW_SETPIXEL_MUL_RGB);
break;
default:
FILLRECT(Uint16, DRAW_SETPIXEL_RGB);
break;
@ -153,6 +168,9 @@ SDL_BlendFillRect_RGB(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGB);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint32, DRAW_SETPIXEL_MUL_RGB);
break;
default:
FILLRECT(Uint32, DRAW_SETPIXEL_RGB);
break;
@ -182,6 +200,9 @@ SDL_BlendFillRect_RGBA(SDL_Surface * dst, const SDL_Rect * rect,
case SDL_BLENDMODE_MOD:
FILLRECT(Uint32, DRAW_SETPIXEL_MOD_RGBA);
break;
case SDL_BLENDMODE_MUL:
FILLRECT(Uint32, DRAW_SETPIXEL_MUL_RGBA);
break;
default:
FILLRECT(Uint32, DRAW_SETPIXEL_RGBA);
break;