Doug Morgan wrote:
>
> Hello,
>
> In Mesa-3.0, glReadPixels doesn't always return the correct alpha values. The
> bug is related to read_fast_rgba_pixels(). In cases where
> (*ctx->Driver.ReadRGBASpan) calls read_color_span, the final returned alpha
> values are all 255, even if there is a local enabled alpha buffer with other
> values. I think a fix might be to in readpix.c change line 507 and beyond from:
>
> for (row=0; row<readHeight; row++) {
> (*ctx->Driver.ReadRGBASpan)(ctx, readWidth, srcX, srcY,
> (void *) dest);
> dest += rowLength * 4;
> srcY++;
> }
>
> to:
> for (row=0; row<readHeight; row++) {
> (*ctx->Driver.ReadRGBASpan)(ctx, readWidth, srcX, srcY,
> (void *) dest);
> if (ctx->RasterMask & ALPHABUF_BIT) {
> gl_read_alpha_span( ctx, readWidth, srcX, srcY, dest );
> }
> dest += rowLength * 4;
> srcY++;
> }
Thanks for the patch and test program. I've commited a fix for
this for Mesa 3.1 (and 3.3).
-Brian
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