+ else if (texImage->_BaseFormat != texBaseFormat) {
+ /* The internal format and the real format differ, so we can't rely
+ * on the unpack functions setting the correct constant values.
+ * (e.g. reading back GL_RGB8 which is actually RGBA won't set alpha=1)
+ */
+ switch (texImage->_BaseFormat) {
+ case GL_RED:
+ if ((texBaseFormat == GL_RGBA ||
+ texBaseFormat == GL_RGB ||
+ texBaseFormat == GL_RG) &&
+ (destBaseFormat == GL_RGBA ||
+ destBaseFormat == GL_RGB ||
+ destBaseFormat == GL_RG ||
+ destBaseFormat == GL_GREEN)) {
+ rebaseFormat = texImage->_BaseFormat;
+ break;
+ }
+ /* fall through */
+ case GL_RG:
+ if ((texBaseFormat == GL_RGBA ||
+ texBaseFormat == GL_RGB) &&
+ (destBaseFormat == GL_RGBA ||
+ destBaseFormat == GL_RGB ||
+ destBaseFormat == GL_BLUE)) {
+ rebaseFormat = texImage->_BaseFormat;
+ break;
+ }
+ /* fall through */
+ case GL_RGB:
+ if (texBaseFormat == GL_RGBA &&
+ (destBaseFormat == GL_RGBA ||
+ destBaseFormat == GL_ALPHA ||
+ destBaseFormat == GL_LUMINANCE_ALPHA)) {
+ rebaseFormat = texImage->_BaseFormat;
+ }
+ break;
+
+ case GL_ALPHA:
+ if (destBaseFormat != GL_ALPHA) {
+ rebaseFormat = texImage->_BaseFormat;
+ }
+ break;
+ }
+ }