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gpu/internal/opengl: add fallback for sparse OpenGL ES 2.0 ReadPixels

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OpenGL ES 2.0 doesn't support GL_PACK_ROW_LENGTH, so this change implements
a fallback using a temporary buffer.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
This commit is contained in:
Elias Naur
2022-04-13 17:14:06 +02:00
parent 43865ddabd
commit 6a14269682
1 changed files with 13 additions and 5 deletions
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gpu/internal/opengl/opengl.go
+13 -5
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@@ -1156,17 +1156,25 @@ func (b *Backend) CopyTexture(dst driver.Texture, dstOrigin image.Point, src dri
func (t *texture) ReadPixels(src image.Rectangle, pixels []byte, stride int) error {
glErr(t.backend.funcs)
t.backend.glstate.bindFramebuffer(t.backend.funcs, gl.FRAMEBUFFER, t.ensureFBO())
if len(pixels) < src.Dx()*src.Dy()*4 {
w, h := src.Dx(), src.Dy()
if len(pixels) < w*h*4 {
return errors.New("unexpected RGBA size")
}
w, h := src.Dx(), src.Dy()
// WebGL 1 doesn't support PACK_ROW_LENGTH != 0. Avoid it if possible.
// OpenGL ES 2 doesn't support PACK_ROW_LENGTH != 0. Avoid it if possible.
rowLen := 0
if n := stride / 4; n != w {
rowLen = n
}
t.backend.glstate.pixelStorei(t.backend.funcs, gl.PACK_ROW_LENGTH, rowLen)
t.backend.funcs.ReadPixels(src.Min.X, src.Min.Y, w, h, gl.RGBA, gl.UNSIGNED_BYTE, pixels)
if rowLen == 0 || t.backend.glver[0] > 2 {
t.backend.glstate.pixelStorei(t.backend.funcs, gl.PACK_ROW_LENGTH, rowLen)
t.backend.funcs.ReadPixels(src.Min.X, src.Min.Y, w, h, gl.RGBA, gl.UNSIGNED_BYTE, pixels)
} else {
tmp := make([]byte, w*h*4)
t.backend.funcs.ReadPixels(src.Min.X, src.Min.Y, w, h, gl.RGBA, gl.UNSIGNED_BYTE, tmp)
for y := 0; y < h; y++ {
copy(pixels[y*stride:], tmp[y*w*4:])
}
}
return glErr(t.backend.funcs)
}