lavc, lavu: move frame cropping to a convenience function

Signed-off-by: Anton Khirnov <anton@khirnov.net>

3 files changed, 135 insertions, 1 deletions

diff --git a/libavutil/frame.c b/libavutil/frame.c
index 9cd5f9ab37..db3897c299 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -596,3 +596,103 @@ void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type)
         }
     }
 }
+
+static int calc_cropping_offsets(size_t offsets[4], const AVFrame *frame,
+                                 const AVPixFmtDescriptor *desc)
+{
+    int i, j;
+
+    for (i = 0; frame->data[i]; i++) {
+        const AVComponentDescriptor *comp = NULL;
+        int shift_x = (i == 1 || i == 2) ? desc->log2_chroma_w : 0;
+        int shift_y = (i == 1 || i == 2) ? desc->log2_chroma_h : 0;
+
+        if (desc->flags & (AV_PIX_FMT_FLAG_PAL | AV_PIX_FMT_FLAG_PSEUDOPAL) && i == 1) {
+            offsets[i] = 0;
+            break;
+        }
+
+        /* find any component descriptor for this plane */
+        for (j = 0; j < desc->nb_components; j++) {
+            if (desc->comp[j].plane == i) {
+                comp = &desc->comp[j];
+                break;
+            }
+        }
+        if (!comp)
+            return AVERROR_BUG;
+
+        offsets[i] = (frame->crop_top  >> shift_y) * frame->linesize[i] +
+                     (frame->crop_left >> shift_x) * comp->step;
+    }
+
+    return 0;
+}
+
+int av_frame_apply_cropping(AVFrame *frame, int flags)
+{
+    const AVPixFmtDescriptor *desc;
+    size_t offsets[4];
+    int i;
+
+    if (!(frame->width > 0 && frame->height > 0))
+        return AVERROR(EINVAL);
+
+    if (frame->crop_left >= INT_MAX - frame->crop_right        ||
+        frame->crop_top  >= INT_MAX - frame->crop_bottom       ||
+        (frame->crop_left + frame->crop_right) >= frame->width ||
+        (frame->crop_top + frame->crop_bottom) >= frame->height)
+        return AVERROR(ERANGE);
+
+    desc = av_pix_fmt_desc_get(frame->format);
+    if (!desc)
+        return AVERROR_BUG;
+
+    /* Apply just the right/bottom cropping for hwaccel formats. Bitstream
+     * formats cannot be easily handled here either (and corresponding decoders
+     * should not export any cropping anyway), so do the same for those as well.
+     * */
+    if (desc->flags & (AV_PIX_FMT_FLAG_BITSTREAM | AV_PIX_FMT_FLAG_HWACCEL)) {
+        frame->width      -= frame->crop_right;
+        frame->height     -= frame->crop_bottom;
+        frame->crop_right  = 0;
+        frame->crop_bottom = 0;
+        return 0;
+    }
+
+    /* calculate the offsets for each plane */
+    calc_cropping_offsets(offsets, frame, desc);
+
+    /* adjust the offsets to avoid breaking alignment */
+    if (!(flags & AV_FRAME_CROP_UNALIGNED)) {
+        int log2_crop_align = frame->crop_left ? av_ctz(frame->crop_left) : INT_MAX;
+        int min_log2_align = INT_MAX;
+
+        for (i = 0; frame->data[i]; i++) {
+            int log2_align = offsets[i] ? av_ctz(offsets[i]) : INT_MAX;
+            min_log2_align = FFMIN(log2_align, min_log2_align);
+        }
+
+        /* we assume, and it should always be true, that the data alignment is
+         * related to the cropping alignment by a constant power-of-2 factor */
+        if (log2_crop_align < min_log2_align)
+            return AVERROR_BUG;
+
+        if (min_log2_align < 5) {
+            frame->crop_left &= ~((1 << (5 + log2_crop_align - min_log2_align)) - 1);
+            calc_cropping_offsets(offsets, frame, desc);
+        }
+    }
+
+    for (i = 0; frame->data[i]; i++)
+        frame->data[i] += offsets[i];
+
+    frame->width      -= (frame->crop_left + frame->crop_right);
+    frame->height     -= (frame->crop_top  + frame->crop_bottom);
+    frame->crop_left   = 0;
+    frame->crop_right  = 0;
+    frame->crop_top    = 0;
+    frame->crop_bottom = 0;
+
+    return 0;
+}
diff --git a/libavutil/frame.h b/libavutil/frame.h
index f9ffb5bbbf..ff3fe46dd6 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -580,6 +580,40 @@ AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
  */
 void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);
 
+
+/**
+ * Flags for frame cropping.
+ */
+enum {
+    /**
+     * Apply the maximum possible cropping, even if it requires setting the
+     * AVFrame.data[] entries to unaligned pointers. Passing unaligned data
+     * to Libav API is generally not allowed, and causes undefined behavior
+     * (such as crashes). You can pass unaligned data only to Libav APIs that
+     * are explicitly documented to accept it. Use this flag only if you
+     * absolutely know what you are doing.
+     */
+    AV_FRAME_CROP_UNALIGNED     = 1 << 0,
+};
+
+/**
+ * Crop the given video AVFrame according to its crop_left/crop_top/crop_right/
+ * crop_bottom fields. If cropping is successful, the function will adjust the
+ * data pointers and the width/height fields, and set the crop fields to 0.
+ *
+ * In all cases, the cropping boundaries will be rounded to the inherent
+ * alignment of the pixel format. In some cases, such as for opaque hwaccel
+ * formats, the left/top cropping is ignored. The crop fields are set to 0 even
+ * if the cropping was rounded or ignored.
+ *
+ * @param frame the frame which should be cropped
+ * @param flags Some combination of AV_FRAME_CROP_* flags, or 0.
+ *
+ * @return >= 0 on success, a negative AVERROR on error. If the cropping fields
+ * were invalid, AVERROR(ERANGE) is returned, and nothing is changed.
+ */
+int av_frame_apply_cropping(AVFrame *frame, int flags);
+
 /**
  * @}
  */
diff --git a/libavutil/version.h b/libavutil/version.h
index 2c85120b64..53bf72efdd 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -54,7 +54,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 56
-#define LIBAVUTIL_VERSION_MINOR  2
+#define LIBAVUTIL_VERSION_MINOR  3
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \