s_blend.c File Reference

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Detailed Description

software blending.

Author:

Brian Paul

Only a few blend modes have been optimized (min, max, transparency, add) more optimized cases can easily be added if needed. Celestia uses glBlendFunc(GL_SRC_ALPHA, GL_ONE), for example.

#include "main/glheader.h"
#include "main/context.h"
#include "main/colormac.h"
#include "main/macros.h"
#include "s_blend.h"
#include "s_context.h"
#include "s_span.h"

Defines
#define	_BLENDAPI
#define	DIV255(X)   (divtemp = (X), ((divtemp << 8) + divtemp + 256) >> 16)
	Integer divide by 255 Declare "int divtemp" before using.
Functions
static void _BLENDAPI	blend_noop (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Special case for glBlendFunc(GL_ZERO, GL_ONE).
static void _BLENDAPI	blend_replace (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Special case for glBlendFunc(GL_ONE, GL_ZERO) Any chanType ok.
static void _BLENDAPI	blend_transparency_ubyte (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Common transparency blending mode: glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA).
static void _BLENDAPI	blend_transparency_ushort (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
static void _BLENDAPI	blend_transparency_float (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
static void _BLENDAPI	blend_add (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Add src and dest: glBlendFunc(GL_ONE, GL_ONE).
static void _BLENDAPI	blend_min (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Blend min function.
static void _BLENDAPI	blend_max (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Blend max function.
static void _BLENDAPI	blend_modulate (GLcontext *ctx, GLuint n, const GLubyte mask[], GLvoid *src, const GLvoid *dst, GLenum chanType)
	Modulate: result = src * dest Any chanType ok.
static void	blend_general_float (GLcontext *ctx, GLuint n, const GLubyte mask[], GLfloat rgba[][4], GLfloat dest[][4], GLenum chanType)
	Do any blending operation, using floating point.
static void	blend_general (GLcontext *ctx, GLuint n, const GLubyte mask[], void *src, const void *dst, GLenum chanType)
	Do any blending operation, any chanType.
void	_swrast_choose_blend_func (GLcontext *ctx, GLenum chanType)
	Analyze current blending parameters to pick fastest blending function.
void	_swrast_blend_span (GLcontext *ctx, struct gl_renderbuffer *rb, SWspan *span)
	Apply the blending operator to a span of pixels.

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Define Documentation

#define _BLENDAPI

#define DIV255

(

X

)

(divtemp = (X), ((divtemp << 8) + divtemp + 256) >> 16)

Integer divide by 255 Declare "int divtemp" before using.

This satisfies Glean and should be reasonably fast. Contributed by Nathan Hand.

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Function Documentation

void _swrast_blend_span	(	GLcontext *	ctx,
		struct gl_renderbuffer *	rb,
		SWspan *	span
	)

Apply the blending operator to a span of pixels.

We can handle horizontal runs of pixels (spans) or arrays of x/y pixel coordinates.

void _swrast_choose_blend_func	(	GLcontext *	ctx,
		GLenum	chanType
	)

Analyze current blending parameters to pick fastest blending function.

Result: the ctx->Color.BlendFunc pointer is updated.

static void _BLENDAPI blend_add	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Add src and dest: glBlendFunc(GL_ONE, GL_ONE).

Any chanType ok.

static void blend_general	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		void *	src,
		const void *	dst,
		GLenum	chanType
	)			[static]

Do any blending operation, any chanType.

static void blend_general_float	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLfloat	rgba[][4],
		GLfloat	dest[][4],
		GLenum	chanType
	)			[static]

Do any blending operation, using floating point.

Parameters:

	n	number of pixels
	mask	fragment writemask array
	rgba	array of incoming (and modified) pixels
	dest	array of pixels from the dest color buffer

static void _BLENDAPI blend_max	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Blend max function.

Any chanType ok.

static void _BLENDAPI blend_min	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Blend min function.

Any chanType ok.

static void _BLENDAPI blend_modulate	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Modulate: result = src * dest Any chanType ok.

static void _BLENDAPI blend_noop	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Special case for glBlendFunc(GL_ZERO, GL_ONE).

No-op means the framebuffer values remain unchanged. Any chanType ok.

static void _BLENDAPI blend_replace	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Special case for glBlendFunc(GL_ONE, GL_ZERO) Any chanType ok.

static void _BLENDAPI blend_transparency_float	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

static void _BLENDAPI blend_transparency_ubyte	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

Common transparency blending mode: glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA).

static void _BLENDAPI blend_transparency_ushort	(	GLcontext *	ctx,
		GLuint	n,
		const GLubyte	mask[],
		GLvoid *	src,
		const GLvoid *	dst,
		GLenum	chanType
	)			[static]

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