Use more accurate conversion for rgb15/16 to rgb24/32 (C/MMX).

Fate update by michael.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 18 insertions, 39 deletions

diff --git a/libswscale/rgb2rgb_template.c b/libswscale/rgb2rgb_template.c
index 0734e8891b..6363bc19aa 100644
--- a/libswscale/rgb2rgb_template.c
+++ b/libswscale/rgb2rgb_template.c
@@ -227,27 +227,6 @@ static inline void rgb24to15_c(const uint8_t *src, uint8_t *dst, int src_size)
     }
 }
 
-/*
-  I use less accurate approximation here by simply left-shifting the input
-  value and filling the low order bits with zeroes. This method improves PNG
-  compression but this scheme cannot reproduce white exactly, since it does
-  not generate an all-ones maximum value; the net effect is to darken the
-  image slightly.
-
-  The better method should be "left bit replication":
-
-   4 3 2 1 0
-   ---------
-   1 1 0 1 1
-
-   7 6 5 4 3  2 1 0
-   ----------------
-   1 1 0 1 1  1 1 0
-   |=======|  |===|
-       |      leftmost bits repeated to fill open bits
-       |
-   original bits
-*/
 static inline void rgb15tobgr24_c(const uint8_t *src, uint8_t *dst, int src_size)
 {
     const uint16_t *end;
@@ -257,9 +236,9 @@ static inline void rgb15tobgr24_c(const uint8_t *src, uint8_t *dst, int src_size
     while (s < end) {
         register uint16_t bgr;
         bgr = *s++;
-        *d++ = (bgr&0x1F)<<3;
-        *d++ = (bgr&0x3E0)>>2;
-        *d++ = (bgr&0x7C00)>>7;
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
+        *d++ = ((bgr&0x3E0)>>2) | ((bgr&0x3E0)>>7);
+        *d++ = ((bgr&0x7C00)>>7) | ((bgr&0x7C00)>>12);
     }
 }
 
@@ -272,9 +251,9 @@ static inline void rgb16tobgr24_c(const uint8_t *src, uint8_t *dst, int src_size
     while (s < end) {
         register uint16_t bgr;
         bgr = *s++;
-        *d++ = (bgr&0x1F)<<3;
-        *d++ = (bgr&0x7E0)>>3;
-        *d++ = (bgr&0xF800)>>8;
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
+        *d++ = ((bgr&0x7E0)>>3) | ((bgr&0x7E0)>>9);
+        *d++ = ((bgr&0xF800)>>8) | ((bgr&0xF800)>>13);
     }
 }
 
@@ -289,13 +268,13 @@ static inline void rgb15to32_c(const uint8_t *src, uint8_t *dst, int src_size)
         bgr = *s++;
 #if HAVE_BIGENDIAN
         *d++ = 255;
-        *d++ = (bgr&0x7C00)>>7;
-        *d++ = (bgr&0x3E0)>>2;
-        *d++ = (bgr&0x1F)<<3;
+        *d++ = ((bgr&0x7C00)>>7) | ((bgr&0x7C00)>>12);
+        *d++ = ((bgr&0x3E0)>>2) | ((bgr&0x3E0)>>7);
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
 #else
-        *d++ = (bgr&0x1F)<<3;
-        *d++ = (bgr&0x3E0)>>2;
-        *d++ = (bgr&0x7C00)>>7;
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
+        *d++ = ((bgr&0x3E0)>>2) | ((bgr&0x3E0)>>7);
+        *d++ = ((bgr&0x7C00)>>7) | ((bgr&0x7C00)>>12);
         *d++ = 255;
 #endif
     }
@@ -312,13 +291,13 @@ static inline void rgb16to32_c(const uint8_t *src, uint8_t *dst, int src_size)
         bgr = *s++;
 #if HAVE_BIGENDIAN
         *d++ = 255;
-        *d++ = (bgr&0xF800)>>8;
-        *d++ = (bgr&0x7E0)>>3;
-        *d++ = (bgr&0x1F)<<3;
+        *d++ = ((bgr&0xF800)>>8) | ((bgr&0xF800)>>13);
+        *d++ = ((bgr&0x7E0)>>3) | ((bgr&0x7E0)>>9);
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
 #else
-        *d++ = (bgr&0x1F)<<3;
-        *d++ = (bgr&0x7E0)>>3;
-        *d++ = (bgr&0xF800)>>8;
+        *d++ = ((bgr&0x1F)<<3) | ((bgr&0x1F)>>2);
+        *d++ = ((bgr&0x7E0)>>3) | ((bgr&0x7E0)>>9);
+        *d++ = ((bgr&0xF800)>>8) | ((bgr&0xF800)>>13);
         *d++ = 255;
 #endif
     }