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[98.224.219.15]) by smtp.gmail.com with ESMTPSA id cd8-20020a0566381a0800b00406521ad090sm3710594jab.94.2023.03.21.20.26.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Mar 2023 20:26:39 -0700 (PDT) From: Leo Izen To: ffmpeg-devel@ffmpeg.org Date: Tue, 21 Mar 2023 23:26:25 -0400 Message-Id: <20230322032626.45777-2-leo.izen@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230322032626.45777-1-leo.izen@gmail.com> References: <20230322032626.45777-1-leo.izen@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH v3 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 | 48 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c index 9403d72f2f..8fbb71f60f 100644 --- a/libavcodec/pngdec.c +++ b/libavcodec/pngdec.c @@ -98,6 +98,7 @@ 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; @@ -716,6 +717,14 @@ static int populate_avctx_color_fields(AVCodecContext *avctx, AVFrame *frame) avctx->colorspace = frame->colorspace = AVCOL_SPC_RGB; avctx->color_range = frame->color_range = AVCOL_RANGE_JPEG; + /* + * tRNS sets alpha depth to full, so we ignore sBIT if set. + * As a result we must wait until now to set + * avctx->bits_per_raw_sample in case tRNS appears after sBIT + */ + if (!s->has_trns && s->significant_bits > 0) + avctx->bits_per_raw_sample = s->significant_bits; + return 0; } @@ -996,6 +1005,41 @@ fail: return ret; } +static int decode_sbit_chunk(AVCodecContext *avctx, PNGDecContext *s, + GetByteContext *gb) +{ + int bits = 0; + int channels; + + if (!(s->hdr_state & PNG_IHDR)) { + av_log(avctx, AV_LOG_ERROR, "sBIT before IHDR\n"); + return AVERROR_INVALIDDATA; + } + + if (s->pic_state & PNG_IDAT) { + av_log(avctx, AV_LOG_ERROR, "sBIT after IDAT\n"); + return AVERROR_INVALIDDATA; + } + + channels = ff_png_get_nb_channels(s->color_type); + + if (bytestream2_get_bytes_left(gb) != channels) + return AVERROR_INVALIDDATA; + + for (int i = 0; i < channels; i++) { + int b = bytestream2_get_byteu(gb); + bits = FFMAX(b, bits); + } + + 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) { @@ -1440,6 +1484,10 @@ static int decode_frame_common(AVCodecContext *avctx, PNGDecContext *s, break; } + case MKTAG('s', 'B', 'I', 'T'): + if ((ret = decode_sbit_chunk(avctx, s, &gb_chunk)) < 0) + goto fail; + break; case MKTAG('g', 'A', 'M', 'A'): { AVBPrint bp; char *gamma_str; -- 2.40.0 _______________________________________________ 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".