1 files changed, 45 insertions, 0 deletions

diff --git a/src/mesa/main/texgetimage.c b/src/mesa/main/texgetimage.c
index d1c00e80039..7299a4b23e9 100644
--- a/src/mesa/main/texgetimage.c
+++ b/src/mesa/main/texgetimage.c
@@ -367,6 +367,7 @@ get_tex_rgba_uncompressed(struct gl_context *ctx, GLuint dimensions,
    GLuint (*rgba_uint)[4];
    GLboolean tex_is_integer = _mesa_is_format_integer_color(texImage->TexFormat);
    GLboolean tex_is_uint = _mesa_is_format_unsigned(texImage->TexFormat);
+   GLenum texBaseFormat = _mesa_get_format_base_format(texImage->TexFormat);
 
    /* Allocate buffer for one row of texels */
    rgba = malloc(4 * width * sizeof(GLfloat));
@@ -403,6 +404,50 @@ get_tex_rgba_uncompressed(struct gl_context *ctx, GLuint dimensions,
        */
       rebaseFormat = GL_LUMINANCE_ALPHA; /* this covers GL_LUMINANCE too */
    }
+   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;
+      }
+   }
 
    for (img = 0; img < depth; img++) {
       GLubyte *srcMap;