Mesa (master): util: Utility function to determine the channels that can be written in a color format .

[Jose Fonseca]

Module: Mesa
Branch: master
Commit: f25b6e546e66955d70a1aa72135a5054c4f0ed3e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f25b6e546e66955d70a1aa72135a5054c4f0ed3e

Author: José Fonseca <jfonseca at vmware.com>
Date:   Fri Sep  3 20:21:33 2010 +0100

util: Utility function to determine the channels that can be written in a color format.

---

 src/gallium/auxiliary/util/u_format.h |   33 +++++++++++++++++++++++++++++++++
 1 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_format.h b/src/gallium/auxiliary/util/u_format.h
index 8e786a3..59bd03b 100644
--- a/src/gallium/auxiliary/util/u_format.h
+++ b/src/gallium/auxiliary/util/u_format.h
@@ -440,6 +440,39 @@ util_format_is_depth_and_stencil(enum pipe_format format)
            desc->swizzle[1] != UTIL_FORMAT_SWIZZLE_NONE) ? TRUE : FALSE;
 }
 
+
+/**
+ * Give the RGBA colormask of the channels that can be represented in this
+ * format.
+ *
+ * That is, the channels whose values are preserved.
+ */
+static INLINE unsigned
+util_format_colormask(const struct util_format_description *desc)
+{
+   unsigned colormask;
+   unsigned chan;
+
+   switch (desc->colorspace) {
+   case UTIL_FORMAT_COLORSPACE_RGB:
+   case UTIL_FORMAT_COLORSPACE_SRGB:
+   case UTIL_FORMAT_COLORSPACE_YUV:
+      colormask = 0;
+      for (chan = 0; chan < 4; ++chan) {
+         if (desc->swizzle[chan] < 4) {
+            colormask |= (1 << chan);
+         }
+      }
+      return colormask;
+   case UTIL_FORMAT_COLORSPACE_ZS:
+      return 0;
+   default:
+      assert(0);
+      return 0;
+   }
+}
+
+
 /**
  * Whether this format is a rgab8 variant.
  *