lavfi/super2xsai: simplify code updating the color matrix at each y iteration

Remove duplicated out-of-loop init code, and do color matrix
initialization at the beginning of each y iteration.

Allow factorization and avoid an useless matrix update in the last
iteration.

libavfilter/vf_super2xsai.c

@@ -74,7 +74,12 @@ static void super2xsai(AVFilterContext *ctx,
 #define READ_COLOR3(dst, src_line, off) dst = AV_RL24 (src_line + 3*off)
 #define READ_COLOR2(dst, src_line, off) dst = *((const uint16_t *)src_line + off)
 
-    /* Initialise the color matrix for this row. */
+    for (y = 0; y < height; y++) {
+        uint8_t *dst_line[2];
+
+        dst_line[0] = dst + dst_linesize*2*y;
+        dst_line[1] = dst + dst_linesize*(2*y+1);
+
         switch (bpp) {
         case 4:
             READ_COLOR4(color[0][0], src_line[0], 0); color[0][1] = color[0][0]; READ_COLOR4(color[0][2], src_line[0], 1); READ_COLOR4(color[0][3], src_line[0], 2);
@@ -95,12 +100,6 @@ static void super2xsai(AVFilterContext *ctx,
             READ_COLOR2(color[3][0], src_line[3], 0); color[3][1] = color[3][0]; READ_COLOR2(color[3][2], src_line[3], 1); READ_COLOR2(color[3][3], src_line[3], 2);
         }
 
-    for (y = 0; y < height; y++) {
-        uint8_t *dst_line[2];
-
-        dst_line[0] = dst + dst_linesize*2*y;
-        dst_line[1] = dst + dst_linesize*(2*y+1);
-
         for (x = 0; x < width; x++) {
             uint32_t product1a, product1b, product2a, product2b;
 
@@ -220,26 +219,6 @@ static void super2xsai(AVFilterContext *ctx,
         src_line[3] = src_line[2];
         if (y < height - 3)
             src_line[3] += src_linesize;
-
-        switch (bpp) {
-        case 4:
-            READ_COLOR4(color[0][0], src_line[0], 0); color[0][1] = color[0][0]; READ_COLOR4(color[0][2], src_line[0], 1); READ_COLOR4(color[0][3], src_line[0], 2);
-            READ_COLOR4(color[1][0], src_line[1], 0); color[1][1] = color[1][0]; READ_COLOR4(color[1][2], src_line[1], 1); READ_COLOR4(color[1][3], src_line[1], 2);
-            READ_COLOR4(color[2][0], src_line[2], 0); color[2][1] = color[2][0]; READ_COLOR4(color[2][2], src_line[2], 1); READ_COLOR4(color[2][3], src_line[2], 2);
-            READ_COLOR4(color[3][0], src_line[3], 0); color[3][1] = color[3][0]; READ_COLOR4(color[3][2], src_line[3], 1); READ_COLOR4(color[3][3], src_line[3], 2);
-            break;
-        case 3:
-            READ_COLOR3(color[0][0], src_line[0], 0); color[0][1] = color[0][0]; READ_COLOR3(color[0][2], src_line[0], 1); READ_COLOR3(color[0][3], src_line[0], 2);
-            READ_COLOR3(color[1][0], src_line[1], 0); color[1][1] = color[1][0]; READ_COLOR3(color[1][2], src_line[1], 1); READ_COLOR3(color[1][3], src_line[1], 2);
-            READ_COLOR3(color[2][0], src_line[2], 0); color[2][1] = color[2][0]; READ_COLOR3(color[2][2], src_line[2], 1); READ_COLOR3(color[2][3], src_line[2], 2);
-            READ_COLOR3(color[3][0], src_line[3], 0); color[3][1] = color[3][0]; READ_COLOR3(color[3][2], src_line[3], 1); READ_COLOR3(color[3][3], src_line[3], 2);
-            break;
-        default:
-            READ_COLOR2(color[0][0], src_line[0], 0); color[0][1] = color[0][0]; READ_COLOR2(color[0][2], src_line[0], 1); READ_COLOR2(color[0][3], src_line[0], 2);
-            READ_COLOR2(color[1][0], src_line[1], 0); color[1][1] = color[1][0]; READ_COLOR2(color[1][2], src_line[1], 1); READ_COLOR2(color[1][3], src_line[1], 2);
-            READ_COLOR2(color[2][0], src_line[2], 0); color[2][1] = color[2][0]; READ_COLOR2(color[2][2], src_line[2], 1); READ_COLOR2(color[2][3], src_line[2], 2);
-            READ_COLOR2(color[3][0], src_line[3], 0); color[3][1] = color[3][0]; READ_COLOR2(color[3][2], src_line[3], 1); READ_COLOR2(color[3][3], src_line[3], 2);
-        }
     } // y loop
 }