SDL/include/SDL_blendmode.h
Sam Lantinga 981e0d367c Fixed bug 4903 - Lack of color multiply with alpha (SDL_BLENDMODE_MOD + SDL_BLENDMODE_BLEND) blending mode for all renderers
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.
2020-01-16 08:52:59 -08:00

124 lines
5.2 KiB
C

/*
Simple DirectMedia Layer
Copyright (C) 1997-2019 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
/**
* \file SDL_blendmode.h
*
* Header file declaring the SDL_BlendMode enumeration
*/
#ifndef SDL_blendmode_h_
#define SDL_blendmode_h_
#include "begin_code.h"
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief The blend mode used in SDL_RenderCopy() and drawing operations.
*/
typedef enum
{
SDL_BLENDMODE_NONE = 0x00000000, /**< no blending
dstRGBA = srcRGBA */
SDL_BLENDMODE_BLEND = 0x00000001, /**< alpha blending
dstRGB = (srcRGB * srcA) + (dstRGB * (1-srcA))
dstA = srcA + (dstA * (1-srcA)) */
SDL_BLENDMODE_ADD = 0x00000002, /**< additive blending
dstRGB = (srcRGB * srcA) + dstRGB
dstA = dstA */
SDL_BLENDMODE_MOD = 0x00000004, /**< color modulate
dstRGB = srcRGB * dstRGB
dstA = dstA */
SDL_BLENDMODE_MUL = 0x00000008, /**< color multiply
dstRGB = (srcRGB * dstRGB) + (dstRGB * (1-srcA))
dstA = (srcA * dstA) + (dstA * (1-srcA)) */
SDL_BLENDMODE_INVALID = 0x7FFFFFFF
/* Additional custom blend modes can be returned by SDL_ComposeCustomBlendMode() */
} SDL_BlendMode;
/**
* \brief The blend operation used when combining source and destination pixel components
*/
typedef enum
{
SDL_BLENDOPERATION_ADD = 0x1, /**< dst + src: supported by all renderers */
SDL_BLENDOPERATION_SUBTRACT = 0x2, /**< dst - src : supported by D3D9, D3D11, OpenGL, OpenGLES */
SDL_BLENDOPERATION_REV_SUBTRACT = 0x3, /**< src - dst : supported by D3D9, D3D11, OpenGL, OpenGLES */
SDL_BLENDOPERATION_MINIMUM = 0x4, /**< min(dst, src) : supported by D3D11 */
SDL_BLENDOPERATION_MAXIMUM = 0x5 /**< max(dst, src) : supported by D3D11 */
} SDL_BlendOperation;
/**
* \brief The normalized factor used to multiply pixel components
*/
typedef enum
{
SDL_BLENDFACTOR_ZERO = 0x1, /**< 0, 0, 0, 0 */
SDL_BLENDFACTOR_ONE = 0x2, /**< 1, 1, 1, 1 */
SDL_BLENDFACTOR_SRC_COLOR = 0x3, /**< srcR, srcG, srcB, srcA */
SDL_BLENDFACTOR_ONE_MINUS_SRC_COLOR = 0x4, /**< 1-srcR, 1-srcG, 1-srcB, 1-srcA */
SDL_BLENDFACTOR_SRC_ALPHA = 0x5, /**< srcA, srcA, srcA, srcA */
SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA = 0x6, /**< 1-srcA, 1-srcA, 1-srcA, 1-srcA */
SDL_BLENDFACTOR_DST_COLOR = 0x7, /**< dstR, dstG, dstB, dstA */
SDL_BLENDFACTOR_ONE_MINUS_DST_COLOR = 0x8, /**< 1-dstR, 1-dstG, 1-dstB, 1-dstA */
SDL_BLENDFACTOR_DST_ALPHA = 0x9, /**< dstA, dstA, dstA, dstA */
SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA = 0xA /**< 1-dstA, 1-dstA, 1-dstA, 1-dstA */
} SDL_BlendFactor;
/**
* \brief Create a custom blend mode, which may or may not be supported by a given renderer
*
* \param srcColorFactor source color factor
* \param dstColorFactor destination color factor
* \param colorOperation color operation
* \param srcAlphaFactor source alpha factor
* \param dstAlphaFactor destination alpha factor
* \param alphaOperation alpha operation
*
* The result of the blend mode operation will be:
* dstRGB = dstRGB * dstColorFactor colorOperation srcRGB * srcColorFactor
* and
* dstA = dstA * dstAlphaFactor alphaOperation srcA * srcAlphaFactor
*/
extern DECLSPEC SDL_BlendMode SDLCALL SDL_ComposeCustomBlendMode(SDL_BlendFactor srcColorFactor,
SDL_BlendFactor dstColorFactor,
SDL_BlendOperation colorOperation,
SDL_BlendFactor srcAlphaFactor,
SDL_BlendFactor dstAlphaFactor,
SDL_BlendOperation alphaOperation);
/* Ends C function definitions when using C++ */
#ifdef __cplusplus
}
#endif
#include "close_code.h"
#endif /* SDL_blendmode_h_ */
/* vi: set ts=4 sw=4 expandtab: */