[FFmpeg-devel] [PATCH v2 0/2] PNG sBIT chunk support

[FFmpeg-devel] [PATCH v2 0/2] PNG sBIT chunk support

[Leo Izen]

Add support to the PNG decoder and encoder to support sBIT chunks,
by using AVCodecContext->bits_per_raw_sample.

Leo Izen (2):
  avcodec/pngdec: support sBIT chunks
  avcodec/pngenc: write sBIT chunks

 libavcodec/pngdec.c  | 45 ++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/pngenc.c  |  6 ++++++
 libavcodec/version.h |  2 +-
 3 files changed, 52 insertions(+), 1 deletion(-)

-- 
2.39.2

_______________________________________________
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".

[FFmpeg-devel] [PATCH v2 1/2] avcodec/pngdec: support sBIT chunks

[Leo Izen]

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 <leo.izen@gmail.com>
---
 libavcodec/pngdec.c  | 45 ++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/version.h |  2 +-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 9403d72f2f..3c91896c9b 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 +1005,38 @@ 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);
+
+    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 +1481,10 @@ 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;
diff --git a/libavcodec/version.h b/libavcodec/version.h
index da54f87887..39dbec0208 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -30,7 +30,7 @@
 #include "version_major.h"
 
 #define LIBAVCODEC_VERSION_MINOR   6
-#define LIBAVCODEC_VERSION_MICRO 100
+#define LIBAVCODEC_VERSION_MICRO 101
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \
-- 
2.39.2

_______________________________________________
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".

Re: [FFmpeg-devel] [PATCH v2 1/2] avcodec/pngdec: support sBIT chunks

[Andreas Rheinhardt]

Leo Izen:
> 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 <leo.izen@gmail.com>
> ---
>  libavcodec/pngdec.c  | 45 ++++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/version.h |  2 +-
>  2 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> index 9403d72f2f..3c91896c9b 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 +1005,38 @@ 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);
> +
> +    for (int i = 0; i < channels; i++) {
> +        int b = bytestream2_get_byteu(gb);

What ensures that there is enough input left?

> +        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 +1481,10 @@ 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;
> diff --git a/libavcodec/version.h b/libavcodec/version.h
> index da54f87887..39dbec0208 100644
> --- a/libavcodec/version.h
> +++ b/libavcodec/version.h
> @@ -30,7 +30,7 @@
>  #include "version_major.h"
>  
>  #define LIBAVCODEC_VERSION_MINOR   6
> -#define LIBAVCODEC_VERSION_MICRO 100
> +#define LIBAVCODEC_VERSION_MICRO 101
>  
>  #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
>                                                 LIBAVCODEC_VERSION_MINOR, \

_______________________________________________
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".

Re: [FFmpeg-devel] [PATCH v2 1/2] avcodec/pngdec: support sBIT chunks

[Leo Izen]

On 3/15/23 21:32, Andreas Rheinhardt wrote:
> Leo Izen:
>> 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 <leo.izen@gmail.com>
>> ---
>>   libavcodec/pngdec.c  | 45 ++++++++++++++++++++++++++++++++++++++++++++
>>   libavcodec/version.h |  2 +-
>>   2 files changed, 46 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
>> index 9403d72f2f..3c91896c9b 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 +1005,38 @@ 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);
>> +
>> +    for (int i = 0; i < channels; i++) {
>> +        int b = bytestream2_get_byteu(gb);
> 
> What ensures that there is enough input left?
> 

Good catch, I missed a call to bytestream2_get_bytes_left.

_______________________________________________
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".

[FFmpeg-devel] [PATCH v2 2/2] avcodec/pngenc: write sBIT chunks

[Leo Izen]

Add support for writing sBIT chunks, which mark the significant
bit depth of the PNG file. This obtains the metadata using the field
bits_per_raw_sample of AVCodecContext.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
---
 libavcodec/pngenc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavcodec/pngenc.c b/libavcodec/pngenc.c
index 1489256d00..21b033ea16 100644
--- a/libavcodec/pngenc.c
+++ b/libavcodec/pngenc.c
@@ -442,6 +442,12 @@ 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);
 
+    if (avctx->bits_per_raw_sample > 0 && avctx->bits_per_raw_sample < s->bit_depth) {
+        int len = ff_png_get_nb_channels(s->color_type);
+        memset(s->buf, avctx->bits_per_raw_sample, len);
+        png_write_chunk(&s->bytestream, MKTAG('s', 'B', 'I', 'T'), s->buf, len);
+    }
+
     /* put the palette if needed, must be after colorspace information */
     if (s->color_type == PNG_COLOR_TYPE_PALETTE) {
         int has_alpha, alpha, i;
-- 
2.39.2

_______________________________________________
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".

Re: [FFmpeg-devel] [PATCH v2 0/2] PNG sBIT chunk support

[Leo Izen]

On 3/8/23 15:03, Leo Izen wrote:
> Add support to the PNG decoder and encoder to support sBIT chunks,
> by using AVCodecContext->bits_per_raw_sample.
> 
> Leo Izen (2):
>    avcodec/pngdec: support sBIT chunks
>    avcodec/pngenc: write sBIT chunks
> 
>   libavcodec/pngdec.c  | 45 ++++++++++++++++++++++++++++++++++++++++++++
>   libavcodec/pngenc.c  |  6 ++++++
>   libavcodec/version.h |  2 +-
>   3 files changed, 52 insertions(+), 1 deletion(-)
> 

Will merge in a few days if there's no other objections or comments.

- Leo Izen (thebombzen)

_______________________________________________
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".