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[68.41.54.207]) by smtp.gmail.com with ESMTPSA id q5-20020a02a305000000b0035678e2e175sm3549891jai.50.2023.01.31.21.41.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Jan 2023 21:41:43 -0800 (PST) From: Leo Izen To: ffmpeg-devel@ffmpeg.org Date: Wed, 1 Feb 2023 00:41:28 -0500 Message-Id: <20230201054129.124226-2-leo.izen@gmail.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230201054129.124226-1-leo.izen@gmail.com> References: <20230201054129.124226-1-leo.izen@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 1/2] avcodec/pngdec: support sBIT chunks X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Leo Izen Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: Add support for reading sBIT chunks, which mark the significant bit depth of the PNG file. This passes the metadata using the field bits_per_raw_sample of AVCodecContext. Signed-off-by: Leo Izen --- libavcodec/pngdec.c | 57 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c index 0d969decf2..48313db671 100644 --- a/libavcodec/pngdec.c +++ b/libavcodec/pngdec.c @@ -97,6 +97,7 @@ typedef struct PNGDecContext { int bpp; int has_trns; uint8_t transparent_color_be[6]; + int significant_bits; uint32_t palette[256]; uint8_t *crow_buf; @@ -916,6 +917,55 @@ fail: return ret; } +static int decode_sbit_chunk(AVCodecContext *avctx, PNGDecContext *s, + GetByteContext *gb) +{ + int bits = 0; + + if (!(s->hdr_state & PNG_IHDR)) { + av_log(avctx, AV_LOG_ERROR, "sBIT before IHDR\n"); + return AVERROR_INVALIDDATA; + } + + switch (s->color_type) { + case 0: + bits = bytestream2_get_byteu(gb); + break; + case 2: + case 3: { + int r = bytestream2_get_byteu(gb); + int g = bytestream2_get_byteu(gb); + int b = bytestream2_get_byteu(gb); + bits = FFMAX3(r, g, b); + break; + } + case 4: { + int y = bytestream2_get_byteu(gb); + int a = bytestream2_get_byteu(gb); + bits = FFMAX(y, a); + break; + } + case 6: { + int r = bytestream2_get_byteu(gb); + int g = bytestream2_get_byteu(gb); + int b = bytestream2_get_byteu(gb); + int a = bytestream2_get_byteu(gb); + bits = FFMAX(FFMAX3(r, g, b), a); + break; + } + default: + return AVERROR_INVALIDDATA; + } + + if (bits < 0 || bits > s->bit_depth) { + av_log(avctx, AV_LOG_ERROR, "Invalid significant bits: %d\n", bits); + return AVERROR_INVALIDDATA; + } + s->significant_bits = bits; + + return 0; +} + static void handle_small_bpp(PNGDecContext *s, AVFrame *p) { if (s->bits_per_pixel == 1 && s->color_type == PNG_COLOR_TYPE_PALETTE) { @@ -1355,6 +1405,9 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s, break; } + case MKTAG('s', 'B', 'I', 'T'): + decode_sbit_chunk(avctx, s, &gb_chunk); + break; case MKTAG('g', 'A', 'M', 'A'): { AVBPrint bp; char *gamma_str; @@ -1560,6 +1613,10 @@ static int output_frame(PNGDecContext *s, AVFrame *f) stereo3d->flags = s->stereo_mode ? 0 : AV_STEREO3D_FLAG_INVERT; } + /* tRNS sets alpha depth to full, so we ignore sBIT if set */ + if (!s->has_trns && s->significant_bits > 0) + avctx->bits_per_raw_sample = s->significant_bits; + FFSWAP(AVDictionary*, f->metadata, s->frame_metadata); return 0; -- 2.39.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".