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/ SDL2::blendmode

NAME

SDL2::blendmode - SDL2 BlendMode Enumerations and Declarations

SYNOPSIS

use SDL2 qw[:blendMode];

DESCRIPTION

SDL2::blendmode

Functions

These may be imported by name or with the :blendMode tag.

SDL_ComposeCustomBlendMode( ... )

Compose a custom blend mode for renderers.

A blend mode controls how the pixels from a drawing operation (source) get combined with the pixels from the render target (destination). First, the components of the source and destination pixels get multiplied with their blend factors. Then, the blend operation takes the two products and calculates the result that will get stored in the render target.

Expressed in pseudocode, it would look like this:

$dstRGB = colorOperation( $srcRGB * $srcColorFactor, $dstRGB * $dstColorFactor );
$dstA   = alphaOperation( $srcA * $srcAlphaFactor, $dstA * $dstAlphaFactor );

Where the functions colorOperation( $src, $dst) and alphaOperation( $src, $dst ) can return one of the following:

- $src + $dst
- $src - $dst
- $dst - $src
- min($src, $dst)
- max($src, $dst)

The red, green, and blue components are always multiplied with the first, second, and third components of the SDL_BlendFactor, respectively. The fourth component is not used.

The alpha component is always multiplied with the fourth component of the SDL_BlendFactor. The other components are not used in the alpha calculation.

Support for these blend modes varies for each renderer. To check if a specific SDL_BlendMode is supported, create a renderer and pass it to either SDL_SetRenderDrawBlendMode or SDL_SetTextureBlendMode. They will return with an error if the blend mode is not supported.

This list describes the support of custom blend modes for each renderer in SDL 2.0.6. All renderers support the four blend modes listed in the SDL_BlendMode enumeration.

direct3d: Supports SDL_BLENDOPERATION_ADD with all factors.
direct3d11: Supports all operations with all factors. However, some factors produce unexpected results with SDL_BLENDOPERATION_MINIMUM and SDL_BLENDOPERATION_MAXIMUM.
opengl: Supports the SDL_BLENDOPERATION_ADD operation with all factors. OpenGL versions 1.1, 1.2, and 1.3 do not work correctly with SDL 2.0.6.
opengles: Supports the SDL_BLENDOPERATION_ADD operation with all factors. Color and alpha factors need to be the same. OpenGL ES 1 implementation specific: May also support SDL_BLENDOPERATION_SUBTRACT and SDL_BLENDOPERATION_REV_SUBTRACT. May support color and alpha operations being different from each other. May support color and alpha factors being different from each other.
opengles2: Supports the SDL_BLENDOPERATION_ADD, SDL_BLENDOPERATION_SUBTRACT, SDL_BLENDOPERATION_REV_SUBTRACT operations with all factors.
psp: No custom blend mode support.
software: No custom blend mode support.

Some renderers do not provide an alpha component for the default render target. The SDL_BLENDFACTOR_DST_ALPHA and SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA factors do not have an effect in this case.

Expected parameters include:

srcColorFactor - the SDL_BlendFactor applied to the red, green, and blue components of the source pixels
dstColorFactor - the SDL_BlendFactor applied to the red, green, and blue components of the destination pixels
colorOperation - the SDL_BlendOperation used to combine the red, green, and blue components of the source and destination pixels
srcAlphaFactor - the SDL_BlendFactor applied to the alpha component of the source pixels
dstAlphaFactor - the SDL_BlendFactor applied to the alpha component of the destination pixels
alphaOperation - the SDL_BlendOperation used to combine the alpha component of the source and destination pixels

Returns an SDL_BlendMode that represents the chosen factors and operations.

Defined Values and Enumerations

These may be imported by name.

SDL_BlendMode

The blend mode used in SDL_RenderCopy( ) and drawing operations. These may be imported by name or with the :blendMode tag.

SDL_BLENDMODE_NONE - no blending
dstRGBA = srcRGBA
SDL_BLENDMODE_BLEND - alpha blending
dstRGB = (srcRGB * srcA) + (dstRGB * (1-srcA))
dstA = srcA + (dstA * (1-srcA))
SDL_BLENDMODE_ADD - additive blending
dstRGB = (srcRGB * srcA) + dstRGB
dstA = dstA
SDL_BLENDMODE_MOD - color modulate
dstRGB = srcRGB * dstRGB
dstA = dstA
SDL_BLENDMODE_MUL - color multiply
dstRGB = (srcRGB * dstRGB) + (dstRGB * (1-srcA))
dstA = (srcA * dstA) + (dstA * (1-srcA))
SDL_BLENDMODE_INVALID

Additional custom blend modes can be returned by SDL_ComposeCustomBlendMode( ... ).

SDL_BlendOperation

The blend operation used when combining source and destination pixel components. These may be imported with the :blendOperation tag.

SDL_BLENDOPERATION_ADD - supported by all renderers
dst + src
SDL_BLENDOPERATION_SUBTRACT - supported by D3D9, D3D11, OpenGL, OpenGLES
dst - src
SDL_BLENDOPERATION_REV_SUBTRACT - supported by D3D9, D3D11, OpenGL, OpenGLES
src - dst
SDL_BLENDOPERATION_MINIMUM - supported by D3D11
min(dst, src)
SDL_BLENDOPERATION_MAXIMUM - supported by D3D11
max(dst, src)

SDL_BlendFactor

The normalized factor used to multiply pixel components. These may be imported with the :blendfactor tag.

SDL_BLENDFACTOR_ZERO - 0, 0, 0, 0
SDL_BLENDFACTOR_ONE - 1, 1, 1, 1
SDL_BLENDFACTOR_SRC_COLOR - srcR, srcG, srcB, srcA
SDL_BLENDFACTOR_ONE_MINUS_SRC_COLOR - 1-srcR, 1-srcG, 1-srcB, 1-srcA
SDL_BLENDFACTOR_SRC_ALPHA - srcA, srcA, srcA, srcA
SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA - 1-srcA, 1-srcA, 1-srcA, 1-srcA
SDL_BLENDFACTOR_DST_COLOR - dstR, dstG, dstB, dstA
SDL_BLENDFACTOR_ONE_MINUS_DST_COLOR - 1-dstR, 1-dstG, 1-dstB, 1-dstA
SDL_BLENDFACTOR_DST_ALPHA - dstA, dstA, dstA, dstA
SDL_BLENDFACTOR_ONE_MINUS_DST_ALPHA - 1-dstA, 1-dstA, 1-dstA, 1-dstA

LICENSE

Copyright (C) Sanko Robinson.

This library is free software; you can redistribute it and/or modify it under the terms found in the Artistic License 2. Other copyrights, terms, and conditions may apply to data transmitted through this module.

AUTHOR

Sanko Robinson <sanko@cpan.org>