Clamp Y to 16 - 235, as the MPEG standard uses.

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@4699 92316355-f0b4-4df1-b90c-862c8a59935f

pipi/filter/yuv.c

@@ -31,7 +31,7 @@ pipi_image_t *pipi_rgb2yuv(pipi_image_t *src)
     pipi_image_t *dst;
     pipi_pixels_t *srcp, *dstp;
     float *srcdata, *dstdata;
-    int x, y, w, h, gray;
+    int x, y, w, h;
 
     w = src->w;
     h = src->h;
@@ -56,16 +56,19 @@ pipi_image_t *pipi_rgb2yuv(pipi_image_t *src)
             a = srcdata[d + 3];
 
             yp = 0.299 * r + 0.587 * g + 0.114 * b;
+            yp = (yp * 220.0 + 16.0) / 255.0;
+
             u = 0.5 - 0.14713 * r - 0.28886 * g + 0.436 * b;
             if (u < 0.0) u = 0.0;
             if (u > 1.0) u = 1.0;
+
             v = 0.5 + 0.615 * r - 0.51499 * g - 0.10001 * b;
             if (v < 0.0) v = 0.0;
             if (v > 1.0) v = 1.0;
 
-            dstdata[d] = v;
-            dstdata[d + 1] = yp;
-            dstdata[d + 2] = u;
+            dstdata[d] = yp;
+            dstdata[d + 1] = u;
+            dstdata[d + 2] = v;
             dstdata[d + 3] = a;
         }
     }
@@ -78,7 +81,7 @@ pipi_image_t *pipi_yuv2rgb(pipi_image_t *src)
     pipi_image_t *dst;
     pipi_pixels_t *srcp, *dstp;
     float *srcdata, *dstdata;
-    int x, y, w, h, gray;
+    int x, y, w, h;
 
     w = src->w;
     h = src->h;
@@ -97,9 +100,9 @@ pipi_image_t *pipi_yuv2rgb(pipi_image_t *src)
             double r, g, b, a, yp, u, v;
             int d = 4 * (y * w + x);
 
-            v = srcdata[d] - 0.5;
-            yp = srcdata[d + 1];
-            u = srcdata[d + 2] - 0.5;
+            yp = (srcdata[d] * 255.0 - 16.0) / 220.0;
+            u = srcdata[d + 1] - 0.5;
+            v = srcdata[d + 2] - 0.5;
             a = srcdata[d + 3];
 
             r = yp + 1.13983 * v;