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avifenc: add --noalpha flag to discard alpha channel on encode #3130

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avifenc: add --noalpha flag to discard alpha channel on encode #3130

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e52cae5
avifenc: add --noalpha flag to discard alpha channel on encode
enyetsuen Mar 24, 2026
9eddece
moved discarding alpha to avifInputReadImage()
enyetsuen Mar 24, 2026
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16 changes: 16 additions & 0 deletions apps/avifenc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,7 @@ typedef struct
avifBool ignoreExif;
avifBool ignoreXMP;
avifBool ignoreColorProfile;
avifBool ignoreAlpha;

// These settings are only relevant when compiled with AVIF_ENABLE_JPEG_GAIN_MAP_CONVERSION.
avifBool qualityGainMapIsConstrained; // true if qualityGainMap explicitly set by the user
Expand Down Expand Up @@ -256,6 +257,7 @@ static void syntaxLong(void)
printf(" --ignore-exif : If the input file contains embedded Exif metadata, ignore it (no-op if absent)\n");
printf(" --ignore-xmp : If the input file contains embedded XMP metadata, ignore it (no-op if absent)\n");
printf(" --ignore-profile,--ignore-icc : If the input file contains an embedded color profile, ignore it (no-op if absent)\n");
printf(" --ignore-alpha,--noalpha : Discard the alpha channel when encoding.\n");
#if defined(AVIF_ENABLE_JPEG_GAIN_MAP_CONVERSION)
printf(" --ignore-gain-map : If the input file contains an embedded gain map, ignore it (no-op if absent)\n");
printf(" --qgain-map Q : Quality for the gain map in %d..%d where %d is lossless\n",
Expand Down Expand Up @@ -526,6 +528,7 @@ static avifBool avifInputReadImage(avifInput * input,
avifBool ignoreColorProfile,
avifBool ignoreExif,
avifBool ignoreXMP,
avifBool ignoreAlpha,
avifBool allowChangingCicp,
avifBool ignoreGainMap,
avifImage * image,
Expand Down Expand Up @@ -633,6 +636,11 @@ static avifBool avifInputReadImage(avifInput * input,
}
return AVIF_FALSE;
}

if (ignoreAlpha) {
dstImage->alphaPlane = NULL;
dstImage->alphaRowBytes = 0;
}
if (!allowChangingCicp) {
// Restore the previous primaries/transfer in case avifReadImage changed them.
dstImage->colorPrimaries = colorPrimariesBefore;
Expand All @@ -658,6 +666,7 @@ static avifBool avifInputReadImage(avifInput * input,
ignoreColorProfile,
ignoreExif,
ignoreXMP,
ignoreAlpha,
allowChangingCicp,
ignoreGainMap,
image,
Expand Down Expand Up @@ -919,6 +928,7 @@ static avifBool avifEncodeRestOfImageSequence(avifEncoder * encoder,
/*ignoreColorProfile=*/AVIF_TRUE,
/*ignoreExif=*/AVIF_TRUE,
/*ignoreXMP=*/AVIF_TRUE,
settings->ignoreAlpha,
/*allowChangingCicp=*/AVIF_FALSE,
/*ignoreGainMap=*/AVIF_TRUE,
nextImage,
Expand Down Expand Up @@ -1021,6 +1031,7 @@ static avifBool avifEncodeRestOfLayeredImage(avifEncoder * encoder,
/*ignoreColorProfile=*/AVIF_TRUE,
/*ignoreExif=*/AVIF_TRUE,
/*ignoreXMP=*/AVIF_TRUE,
settings->ignoreAlpha,
!settings->cicpExplicitlySet,
/*ignoreGainMap=*/AVIF_TRUE,
nextImage,
Expand Down Expand Up @@ -1418,6 +1429,7 @@ int main(int argc, char * argv[])
settings.ignoreExif = AVIF_FALSE;
settings.ignoreXMP = AVIF_FALSE;
settings.ignoreColorProfile = AVIF_FALSE;
settings.ignoreAlpha = AVIF_FALSE;
settings.ignoreGainMap = AVIF_FALSE;
settings.cicpExplicitlySet = AVIF_FALSE;
settings.inputFormat = AVIF_APP_FILE_FORMAT_UNKNOWN;
Expand Down Expand Up @@ -1824,6 +1836,8 @@ int main(int argc, char * argv[])
goto cleanup;
}
settings.ignoreColorProfile = AVIF_TRUE;
} else if (!strcmp(arg, "--ignore-alpha") || !strcmp(arg, "--noalpha")) {
settings.ignoreAlpha = AVIF_TRUE;
} else if (!strcmp(arg, "--duration") || strpre(arg, "--duration:")) {
// --duration is special, we always treat it as suffixed with :u, so don't print warning for it.
avifOptionSuffixType type = parseOptionSuffix(arg, /*warnNoSuffix=*/AVIF_FALSE);
Expand Down Expand Up @@ -2317,6 +2331,7 @@ int main(int argc, char * argv[])
settings.ignoreColorProfile,
settings.ignoreExif,
settings.ignoreXMP,
settings.ignoreAlpha,
/*allowChangingCicp=*/!settings.cicpExplicitlySet,
ignoreGainMap,
image,
Expand Down Expand Up @@ -2562,6 +2577,7 @@ int main(int argc, char * argv[])
/*ignoreColorProfile=*/AVIF_TRUE,
/*ignoreExif=*/AVIF_TRUE,
/*ignoreXMP=*/AVIF_TRUE,
settings.ignoreAlpha,
/*allowChangingCicp=*/AVIF_FALSE,
settings.ignoreGainMap,
cellImage,
Expand Down
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