[freetype2-demos] master 4ec7c98: [graph] Explain the blender cache.

[Werner Lemberg]

branch: master
commit 4ec7c98fe55722c8294901f3ae16cd8cb2e9cedc
Author: Alexei Podtelezhnikov <apodtele@gmail.com>
Commit: Alexei Podtelezhnikov <apodtele@gmail.com>

    [graph] Explain the blender cache.
---
 graph/gblblit.c  | 11 +++++++----
 graph/gblender.c | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/graph/gblblit.c b/graph/gblblit.c
index a33015b..5499bd8 100644
--- a/graph/gblblit.c
+++ b/graph/gblblit.c
@@ -9,13 +9,16 @@
 /*                                                                          */
 /****************************************************************************/
 
+/* The cached color gradients from the back- to foreground color are used
+ * to quickly look up the blended color for a given pixel coverage (alpha).
+ * They are calculated with gamma correction and stored with 8-bit depth
+ * per channel, in the range [0-255]. Other supported color representations
+ * require scaling to utilize the cache.
+ */
 
 #include "grobjs.h"
 #include "gblblit.h"
 
-/* blitting gray glyphs
- */
-
 /* generic macros
  */
 #define  GRGB_PACK(r,g,b)      ( ((GBlenderPixel)(r) << 16) | \
@@ -206,7 +209,7 @@
 
 #include "gblany.h"
 
-/* Gray8 blitting routines
+/* Gray8 blitting routines, only 8-bit gray is supported
  */
 #define  GDST_TYPE               gray8
 #define  GDST_INCR               1
diff --git a/graph/gblender.c b/graph/gblender.c
index 309240f..794cf44 100644
--- a/graph/gblender.c
+++ b/graph/gblender.c
@@ -1,3 +1,21 @@
+/****************************************************************************/
+/*                                                                          */
+/*  The FreeType project -- a free and portable quality TrueType renderer.  */
+/*                                                                          */
+/*  Copyright (C) 1996-2023 by                                              */
+/*  D. Turner, R.Wilhelm, and W. Lemberg                                    */
+/*                                                                          */
+/*  gblender.c: Alpha blending with gamma correction and caching.           */
+/*                                                                          */
+/****************************************************************************/
+
+/* The cached color gradients from the back- to foreground color are used
+ * to quickly look up the blended color for a given pixel coverage (alpha).
+ * They are calculated with gamma correction and stored with 8-bit depth
+ * per channel, in the range [0-255]. Other supported color representations
+ * require scaling to utilize the cache.
+ */
+
 #include "gblender.h"
 #include <stdlib.h>