avfilter/vf_eq: add support for alpha channel

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

libavfilter/vf_eq.c

@@ -236,9 +236,9 @@ static const enum AVPixelFormat pixel_fmts_eq[] = {
     AV_PIX_FMT_GRAY8,
     AV_PIX_FMT_YUV410P,
     AV_PIX_FMT_YUV411P,
-    AV_PIX_FMT_YUV420P,
-    AV_PIX_FMT_YUV422P,
-    AV_PIX_FMT_YUV444P,
+    AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUVA422P,
+    AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUVA444P,
     AV_PIX_FMT_NONE
 };
 
@@ -281,11 +281,12 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
             h = AV_CEIL_RSHIFT(h, desc->log2_chroma_h);
         }
 
-        if (eq->param[i].adjust)
-            eq->param[i].adjust(&eq->param[i], out->data[i], out->linesize[i],
+        if (i == 3 || !eq->param[i].adjust)
+            av_image_copy_plane(out->data[i], out->linesize[i],
                                 in->data[i], in->linesize[i], w, h);
+
         else
-            av_image_copy_plane(out->data[i], out->linesize[i],
+            eq->param[i].adjust(&eq->param[i], out->data[i], out->linesize[i],
                                  in->data[i], in->linesize[i], w, h);
     }