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cogl_read_pixels: Always use GL_RGBA/GL_UNSIGNED_BYTE under GLES

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Under GLES glReadPixels is documented to only support GL_RGBA with
GL_UNSIGNED_BYTE and an implementation specfic format which can be
fetched with glGet, GL_IMPLEMENTATION_COLOR_READ_FORMAT_OES and
GL_IMPLEMENTATION_COLOR_READ_TYPE_OES. This patch makes it always read
using GL_RGBA and GL_UNSIGNED_BYTE and then convert the results if
neccessary.

This has some room for improvement because it doesn't attempt to use
the implementation specific format. Also the conversion is somewhat
wasteful because there are currently no cogl_bitmap_* functions to
convert without allocating a new buffer so it ends up doing an
intermediate copy.

http://bugzilla.openedhand.com/show_bug.cgi?id=2057
This commit is contained in:
Neil Roberts 2010-03-26 22:40:53 +00:00
parent f944d419a3
commit 7f629f626e
1 changed files with 58 additions and 9 deletions
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67
cogl/cogl.c
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@ -685,18 +685,67 @@ cogl_read_pixels (int x,
bmp.format |= COGL_PREMULT_BIT;
}
/* Setup the pixel store parameters that may have been changed by
Cogl */
_cogl_texture_driver_prep_gl_for_pixels_download (bmp.rowstride, bpp);
_cogl_pixel_format_to_gl (format, &gl_intformat, &gl_format, &gl_type);
GE (glReadPixels (x, y, width, height, gl_format, gl_type, pixels));
/* Under GLES only GL_RGBA with GL_UNSIGNED_BYTE as well as an
implementation specific format under
GL_IMPLEMENTATION_COLOR_READ_FORMAT_OES and
GL_IMPLEMENTATION_COLOR_READ_TYPE_OES is supported. We could try
to be more clever and check if the requested type matches that
but we would need some reliable functions to convert from GL
types to Cogl types. For now, lets just always read in
GL_RGBA/GL_UNSIGNED_BYTE and convert if necessary */
#ifndef COGL_HAS_GL
if (gl_format != GL_RGBA || gl_type != GL_UNSIGNED_BYTE)
{
CoglBitmap tmp_bmp, dst_bmp;
/* Convert to the premult format specified by the caller
in-place. This will do nothing if the premult status is already
correct. */
_cogl_bitmap_convert_premult_status (&bmp, format);
tmp_bmp.format = COGL_PIXEL_FORMAT_RGBA_8888_PRE;
tmp_bmp.data = g_malloc (width * height * 4);
tmp_bmp.width = width;
tmp_bmp.height = height;
tmp_bmp.rowstride = 4 * width;
_cogl_texture_driver_prep_gl_for_pixels_download (tmp_bmp.rowstride, 4);
GE( glReadPixels (x, y, width, height,
GL_RGBA, GL_UNSIGNED_BYTE,
tmp_bmp.data) );
/* CoglBitmap doesn't currently have a way to convert without
allocating its own buffer so we have to copy the data
again */
if (_cogl_bitmap_convert_format_and_premult (&tmp_bmp,
&dst_bmp,
bmp.format))
{
_cogl_bitmap_copy_subregion (&dst_bmp,
&bmp,
0, 0,
0, 0,
bmp.width, bmp.height);
g_free (dst_bmp.data);
}
else
{
/* FIXME: there's no way to report an error here so we'll
just have to leave the data initialised */
}
g_free (tmp_bmp.data);
}
else
#endif
{
_cogl_texture_driver_prep_gl_for_pixels_download (bmp.rowstride, bpp);
GE( glReadPixels (x, y, width, height, gl_format, gl_type, pixels) );
/* Convert to the premult format specified by the caller
in-place. This will do nothing if the premult status is already
correct. */
_cogl_bitmap_convert_premult_status (&bmp, format);
}
/* NB: All offscreen rendering is done upside down so there is no need
* to flip in this case... */