swscale: Implement alphablendaway for planar 4:4:4 formats

Fixes Ticket4746

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

1 files changed, 74 insertions, 0 deletions

diff --git a/libswscale/alphablend.c b/libswscale/alphablend.c
new file mode 100644
index 0000000000..5833653b83
--- /dev/null
+++ b/libswscale/alphablend.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2015 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "swscale_internal.h"
+
+int ff_sws_alphablendaway(SwsContext *c, const uint8_t *src[],
+                          int srcStride[], int srcSliceY, int srcSliceH,
+                          uint8_t *dst[], int dstStride[])
+{
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(c->srcFormat);
+    int nb_components = desc->nb_components;
+    int plane, x, y;
+    int plane_count = isGray(c->srcFormat) ? 1 : 3;
+    int sixteen_bits = desc->comp[0].depth_minus1 >= 8;
+    unsigned off    = 1<<desc->comp[0].depth_minus1;
+    unsigned shift  = desc->comp[0].depth_minus1 + 1;
+    unsigned max    = (1<<shift) - 1;
+
+    av_assert0(plane_count == nb_components - 1);
+    if (desc->flags & AV_PIX_FMT_FLAG_PLANAR) {
+        for (plane = 0; plane < plane_count; plane++) {
+            int w = plane ? c->chrSrcW : c->srcW;
+            int y_subsample = plane ? desc->log2_chroma_h: 0;
+            for (y = srcSliceY >> y_subsample; y < FF_CEIL_RSHIFT(srcSliceH, y_subsample); y++) {
+                if (sixteen_bits) {
+                    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 = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 1<<desc->comp[0].depth_minus1 : 0;
+                    if ((!isBE(c->dstFormat)) == !HAVE_BIGENDIAN) {
+                        for (x = 0; x < w; x++) {
+                            unsigned u = s[x]*a[x] + target*(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;
+                            d[x] = av_clip((u + (u >> shift)) >> shift, 0, max);
+                        }
+                    }
+                } else {
+                    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 = plane && !(desc->flags & AV_PIX_FMT_FLAG_RGB) ? 128 : 0;
+                    for (x = 0; x < w; x++) {
+                        unsigned u = s[x]*a[x] + target*(255-a[x]) + 128;
+                        d[x] = (257*u) >> 16;
+                    }
+                }
+            }
+        }
+    }
+
+    return 0;
+}