swscale/alphablend: Support SWS_ALPHA_BLEND_CHECKERBOARD

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 16 insertions, 11 deletions

diff --git a/libswscale/alphablend.c b/libswscale/alphablend.c
index 7c9fe6f372..3bd71bac96 100644
--- a/libswscale/alphablend.c
+++ b/libswscale/alphablend.c
@@ -32,10 +32,17 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
     unsigned off    = 1<<desc->comp[0].depth_minus1;
     unsigned shift  = desc->comp[0].depth_minus1 + 1;
     unsigned max    = (1<<shift) - 1;
-    int target_table[3];
+    int target_table[2][3];
 
-    for (plane = 0; plane < plane_count; plane++)
-        target_table[plane] = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<desc->comp[0].depth_minus1 : 0;
+    for (plane = 0; plane < plane_count; plane++) {
+        int a = 0, b = 0;
+        if (c->alphablend == SWS_ALPHA_BLEND_CHECKERBOARD) {
+            a = (1<<desc->comp[0].depth_minus1)/2;
+            b = 3*(1<<desc->comp[0].depth_minus1)/2;
+        }
+        target_table[0][plane] = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<desc->comp[0].depth_minus1 : a;
+        target_table[1][plane] = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<desc->comp[0].depth_minus1 : b;
+    }
 
     av_assert0(plane_count == nb_components - 1);
     if (desc->flags & AV_PIX_FMT_FLAG_PLANAR) {
@@ -47,16 +54,15 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
                     const uint16_t *s = src[plane      ] + srcStride[plane] * y;
                     const uint16_t *a = src[plane_count] + srcStride[plane_count] * y;
                           uint16_t *d = dst[plane      ] + dstStride[plane] * y;
-                    unsigned target = target_table[plane];
                     if ((!isBE(c->srcFormat)) == !HAVE_BIGENDIAN) {
                         for (x = 0; x < w; x++) {
-                            unsigned u = s[x]*a[x] + target*(max-a[x]) + off;
+                            unsigned u = s[x]*a[x] + target_table[((x^y)>>5)&1][plane]*(max-a[x]) + off;
                             d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
                         }
                     } else {
                         for (x = 0; x < w; x++) {
                             unsigned aswap =av_bswap16(a[x]);
-                            unsigned u = av_bswap16(s[x])*aswap + target*(max-aswap) + off;
+                            unsigned u = av_bswap16(s[x])*aswap + target_table[((x^y)>>5)&1][plane]*(max-aswap) + off;
                             d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
                         }
                     }
@@ -64,9 +70,8 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
                     const uint8_t *s = src[plane      ] + srcStride[plane] * y;
                     const uint8_t *a = src[plane_count] + srcStride[plane_count] * y;
                           uint8_t *d = dst[plane      ] + dstStride[plane] * y;
-                    unsigned target = target_table[plane];
                     for (x = 0; x < w; x++) {
-                        unsigned u = s[x]*a[x] + target*(255-a[x]) + 128;
+                        unsigned u = s[x]*a[x] + target_table[((x^y)>>5)&1][plane]*(255-a[x]) + 128;
                         d[x] = (257*u) >> 16;
                     }
                 }
@@ -84,7 +89,7 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
                     for (x = 0; x < w; x++) {
                         for (plane = 0; plane < plane_count; plane++) {
                             int x_index = (plane_count + 1) * x;
-                            unsigned u = s[x_index + plane]*a[x_index] + target_table[plane]*(max-a[x_index]) + off;
+                            unsigned u = s[x_index + plane]*a[x_index] + target_table[((x^y)>>5)&1][plane]*(max-a[x_index]) + off;
                             d[plane_count*x + plane] = av_clip((u + (u >> shift)) >> shift, 0, max);
                         }
                     }
@@ -93,7 +98,7 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
                         for (plane = 0; plane < plane_count; plane++) {
                             int x_index = (plane_count + 1) * x;
                             unsigned aswap =av_bswap16(a[x_index]);
-                            unsigned u = av_bswap16(s[x_index + plane])*aswap + target_table[plane]*(max-aswap) + off;
+                            unsigned u = av_bswap16(s[x_index + plane])*aswap + target_table[((x^y)>>5)&1][plane]*(max-aswap) + off;
                             d[plane_count*x + plane] = av_clip((u + (u >> shift)) >> shift, 0, max);
                         }
                     }
@@ -105,7 +110,7 @@ int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
                 for (x = 0; x < w; x++) {
                     for (plane = 0; plane < plane_count; plane++) {
                         int x_index = (plane_count + 1) * x;
-                        unsigned u = s[x_index + plane]*a[x_index] + target_table[plane]*(255-a[x_index]) + 128;
+                        unsigned u = s[x_index + plane]*a[x_index] + target_table[((x^y)>>5)&1][plane]*(255-a[x_index]) + 128;
                         d[plane_count*x + plane] = (257*u) >> 16;
                     }
                 }