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mesa: add a couple fast-paths to fast_read_rgba_pixels_memcpy()

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Accelerates a few glReadPixels cases for WebGL.
See https://bugs.freedesktop.org/show_bug.cgi?id=48545

v2: Per Jose, use bit twiddling for the swizzle case instead of ubyte
arrays (it's about 44% faster).

Note: This is a candidate for the 8.0 branch.

Reviewed-by: José Fonseca <jfonseca@vmware.com>
This commit is contained in:
Brian Paul 2012-04-17 10:49:16 -06:00
parent b814506e87
commit a5e95a419e
1 changed files with 54 additions and 6 deletions
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60
src/mesa/main/readpix.c
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@ -208,6 +208,11 @@ read_stencil_pixels( struct gl_context *ctx,
ctx->Driver.UnmapRenderbuffer(ctx, rb);
}
/**
* Try to do glReadPixels of RGBA data using a simple memcpy or swizzle.
* \return GL_TRUE if successful, GL_FALSE otherwise (use the slow path)
*/
static GLboolean
fast_read_rgba_pixels_memcpy( struct gl_context *ctx,
GLint x, GLint y,
@ -220,9 +225,23 @@ fast_read_rgba_pixels_memcpy( struct gl_context *ctx,
struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
GLubyte *dst, *map;
int dstStride, stride, j, texelBytes;
GLboolean swizzle_rb = GL_FALSE, copy_xrgb = GL_FALSE;
if (!_mesa_format_matches_format_and_type(rb->Format, format, type,
ctx->Pack.SwapBytes))
/* XXX we could check for other swizzle/special cases here as needed */
if (rb->Format == MESA_FORMAT_RGBA8888_REV &&
format == GL_BGRA &&
type == GL_UNSIGNED_INT_8_8_8_8_REV &&
!ctx->Pack.SwapBytes) {
swizzle_rb = GL_TRUE;
}
else if (rb->Format == MESA_FORMAT_XRGB8888 &&
format == GL_BGRA &&
type == GL_UNSIGNED_INT_8_8_8_8_REV &&
!ctx->Pack.SwapBytes) {
copy_xrgb = GL_TRUE;
}
else if (!_mesa_format_matches_format_and_type(rb->Format, format, type,
ctx->Pack.SwapBytes))
return GL_FALSE;
/* If the format is unsigned normalized then we can ignore clamping
@ -247,10 +266,39 @@ fast_read_rgba_pixels_memcpy( struct gl_context *ctx,
}
texelBytes = _mesa_get_format_bytes(rb->Format);
for (j = 0; j < height; j++) {
memcpy(dst, map, width * texelBytes);
dst += dstStride;
map += stride;
if (swizzle_rb) {
/* swap R/B */
for (j = 0; j < height; j++) {
int i;
for (i = 0; i < width; i++) {
GLuint *dst4 = (GLuint *) dst, *map4 = (GLuint *) map;
GLuint pixel = map4[i];
dst4[i] = (pixel & 0xff00ff00)
| ((pixel & 0x00ff0000) >> 16)
| ((pixel & 0x000000ff) << 16);
}
dst += dstStride;
map += stride;
}
} else if (copy_xrgb) {
/* convert xrgb -> argb */
for (j = 0; j < height; j++) {
GLuint *dst4 = (GLuint *) dst, *map4 = (GLuint *) map;
int i;
for (i = 0; i < width; i++) {
dst4[i] = map4[i] | 0xff000000; /* set A=0xff */
}
dst += dstStride;
map += stride;
}
} else {
/* just memcpy */
for (j = 0; j < height; j++) {
memcpy(dst, map, width * texelBytes);
dst += dstStride;
map += stride;
}
}
ctx->Driver.UnmapRenderbuffer(ctx, rb);