avcodec/pngenc: support writing iCCP chunks

We re-use the PNGEncContext.zstream for deflate-related operations.
Other than that, the code is pretty straightforward. Special care needs
to be taken to avoid writing more than 79 characters of the profile
description (the maximum supported).

To write the (dynamically sized) deflate-encoded data, we allocate extra
space in the packet and use that directly as a scratch buffer. Modify
png_write_chunk slightly to allow pre-writing the chunk contents like
this.

Also add a FATE transcode test to ensure that the ICC profile gets
encoded correctly.

Signed-off-by: Niklas Haas <git@haasn.dev>

1 files changed, 82 insertions, 2 deletions

diff --git a/libavcodec/pngenc.c b/libavcodec/pngenc.c
index aaa6453218..d79b4e3895 100644
--- a/libavcodec/pngenc.c
+++ b/libavcodec/pngenc.c
@@ -236,7 +236,8 @@ static void png_write_chunk(uint8_t **f, uint32_t tag,
     bytestream_put_be32(f, av_bswap32(tag));
     if (length > 0) {
         crc = av_crc(crc_table, crc, buf, length);
-        memcpy(*f, buf, length);
+        if (*f != buf)
+            memcpy(*f, buf, length);
         *f += length;
     }
     bytestream_put_be32(f, ~crc);
@@ -345,10 +346,53 @@ static int png_get_gama(enum AVColorTransferCharacteristic trc, uint8_t *buf)
     return 1;
 }
 
+static int png_write_iccp(PNGEncContext *s, const AVFrameSideData *sd)
+{
+    z_stream *const zstream = &s->zstream.zstream;
+    const AVDictionaryEntry *entry;
+    const char *name;
+    uint8_t *start, *buf;
+    int ret;
+
+    if (!sd || !sd->size)
+        return 0;
+    zstream->next_in  = sd->data;
+    zstream->avail_in = sd->size;
+
+    /* write the chunk contents first */
+    start = s->bytestream + 8; /* make room for iCCP tag + length */
+    buf = start;
+
+    /* profile description */
+    entry = av_dict_get(sd->metadata, "name", NULL, 0);
+    name = (entry && entry->value[0]) ? entry->value : "icc";
+    for (int i = 0;; i++) {
+        char c = (i == 79) ? 0 : name[i];
+        bytestream_put_byte(&buf, c);
+        if (!c)
+            break;
+    }
+
+    /* compression method and profile data */
+    bytestream_put_byte(&buf, 0);
+    zstream->next_out  = buf;
+    zstream->avail_out = s->bytestream_end - buf;
+    ret = deflate(zstream, Z_FINISH);
+    deflateReset(zstream);
+    if (ret != Z_STREAM_END)
+        return AVERROR_EXTERNAL;
+
+    /* rewind to the start and write the chunk header/crc */
+    png_write_chunk(&s->bytestream, MKTAG('i', 'C', 'C', 'P'), start,
+                    zstream->next_out - start);
+    return 0;
+}
+
 static int encode_headers(AVCodecContext *avctx, const AVFrame *pict)
 {
     AVFrameSideData *side_data;
     PNGEncContext *s = avctx->priv_data;
+    int ret;
 
     /* write png header */
     AV_WB32(s->buf, avctx->width);
@@ -401,7 +445,11 @@ static int encode_headers(AVCodecContext *avctx, const AVFrame *pict)
     if (png_get_gama(pict->color_trc, s->buf))
         png_write_chunk(&s->bytestream, MKTAG('g', 'A', 'M', 'A'), s->buf, 4);
 
-    /* put the palette if needed */
+    side_data = av_frame_get_side_data(pict, AV_FRAME_DATA_ICC_PROFILE);
+    if ((ret = png_write_iccp(s, side_data)))
+        return ret;
+
+    /* put the palette if needed, must be after colorspace information */
     if (s->color_type == PNG_COLOR_TYPE_PALETTE) {
         int has_alpha, alpha, i;
         unsigned int v;
@@ -525,6 +573,34 @@ the_end:
     return ret;
 }
 
+static int add_icc_profile_size(AVCodecContext *avctx, const AVFrame *pict,
+                                uint64_t *max_packet_size)
+{
+    PNGEncContext *s = avctx->priv_data;
+    const AVFrameSideData *sd;
+    const int hdr_size = 128;
+    uint64_t new_pkt_size;
+    uLong bound;
+
+    if (!pict)
+        return 0;
+    sd = av_frame_get_side_data(pict, AV_FRAME_DATA_ICC_PROFILE);
+    if (!sd || !sd->size)
+        return 0;
+    if (sd->size != (uLong) sd->size)
+        return AVERROR_INVALIDDATA;
+
+    bound = deflateBound(&s->zstream.zstream, sd->size);
+    if (bound > INT32_MAX - hdr_size)
+        return AVERROR_INVALIDDATA;
+
+    new_pkt_size = *max_packet_size + bound + hdr_size;
+    if (new_pkt_size < *max_packet_size)
+        return AVERROR_INVALIDDATA;
+    *max_packet_size = new_pkt_size;
+    return 0;
+}
+
 static int encode_png(AVCodecContext *avctx, AVPacket *pkt,
                       const AVFrame *pict, int *got_packet)
 {
@@ -541,6 +617,8 @@ static int encode_png(AVCodecContext *avctx, AVPacket *pkt,
             enc_row_size +
             12 * (((int64_t)enc_row_size + IOBUF_SIZE - 1) / IOBUF_SIZE) // IDAT * ceil(enc_row_size / IOBUF_SIZE)
         );
+    if ((ret = add_icc_profile_size(avctx, pict, &max_packet_size)))
+        return ret;
     ret = ff_alloc_packet(avctx, pkt, max_packet_size);
     if (ret < 0)
         return ret;
@@ -870,6 +948,8 @@ static int encode_apng(AVCodecContext *avctx, AVPacket *pkt,
             enc_row_size +
             (4 + 12) * (((int64_t)enc_row_size + IOBUF_SIZE - 1) / IOBUF_SIZE) // fdAT * ceil(enc_row_size / IOBUF_SIZE)
         );
+    if ((ret = add_icc_profile_size(avctx, pict, &max_packet_size)))
+        return ret;
     if (max_packet_size > INT_MAX)
         return AVERROR(ENOMEM);