@@ -89,6 +89,11 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
8989 /// </summary>
9090 private JFifMarker jFif ;
9191
92+ /// <summary>
93+ /// Whether the image has a JFIF marker. This is needed to determine, if the colorspace is YCbCr.
94+ /// </summary>
95+ private bool hasJFif ;
96+
9297 /// <summary>
9398 /// Contains information about the Adobe marker.
9499 /// </summary>
@@ -488,27 +493,75 @@ private JpegColorSpace DeduceJpegColorSpace(byte componentCount)
488493
489494 if ( componentCount == 3 )
490495 {
491- if ( ! this . adobe . Equals ( default ) && this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformUnknown )
496+ // We prioritize adobe marker over jfif marker, if somebody really encoded this image with redundant adobe marker,
497+ // then it's most likely an adobe jfif image.
498+ if ( ! this . adobe . Equals ( default ) )
492499 {
493- return JpegColorSpace . RGB ;
500+ if ( this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformYCbCr )
501+ {
502+ return JpegColorSpace . YCbCr ;
503+ }
504+
505+ if ( this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformUnknown )
506+ {
507+ return JpegColorSpace . RGB ;
508+ }
509+
510+ // Fallback to the id color deduction: If these values are 1-3 for a 3-channel image, then the image is assumed to be YCbCr.
511+ if ( this . Components [ 2 ] . Id == 3 && this . Components [ 1 ] . Id == 2 && this . Components [ 0 ] . Id == 1 )
512+ {
513+ return JpegColorSpace . YCbCr ;
514+ }
515+
516+ JpegThrowHelper . ThrowNotSupportedColorSpace ( ) ;
517+ }
518+
519+ if ( this . hasJFif )
520+ {
521+ // JFIF implies YCbCr.
522+ return JpegColorSpace . YCbCr ;
494523 }
495524
525+ // Fallback to the id color deduction.
496526 // If the component Id's are R, G, B in ASCII the colorspace is RGB and not YCbCr.
527+ // See: https://docs.oracle.com/javase/7/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html#color
497528 if ( this . Components [ 2 ] . Id == 66 && this . Components [ 1 ] . Id == 71 && this . Components [ 0 ] . Id == 82 )
498529 {
499530 return JpegColorSpace . RGB ;
500531 }
501532
533+ // 3-channel non-subsampled images are assumed to be RGB.
534+ if ( this . Components [ 2 ] . VerticalSamplingFactor == 1 && this . Components [ 1 ] . VerticalSamplingFactor == 1 && this . Components [ 0 ] . VerticalSamplingFactor == 1 &&
535+ this . Components [ 2 ] . HorizontalSamplingFactor == 1 && this . Components [ 1 ] . HorizontalSamplingFactor == 1 && this . Components [ 0 ] . HorizontalSamplingFactor == 1 )
536+ {
537+ return JpegColorSpace . RGB ;
538+ }
539+
502540 // Some images are poorly encoded and contain incorrect colorspace transform metadata.
503541 // We ignore that and always fall back to the default colorspace.
504542 return JpegColorSpace . YCbCr ;
505543 }
506544
507545 if ( componentCount == 4 )
508546 {
509- return this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformYcck
510- ? JpegColorSpace . Ycck
511- : JpegColorSpace . Cmyk ;
547+ // jfif images doesn't not support 4 component images, so we only check adobe.
548+ if ( ! this . adobe . Equals ( default ) )
549+ {
550+ if ( this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformYcck )
551+ {
552+ return JpegColorSpace . Ycck ;
553+ }
554+
555+ if ( this . adobe . ColorTransform == JpegConstants . Adobe . ColorTransformUnknown )
556+ {
557+ return JpegColorSpace . Cmyk ;
558+ }
559+
560+ JpegThrowHelper . ThrowNotSupportedColorSpace ( ) ;
561+ }
562+
563+ // Fallback to cmyk as neither of cmyk nor ycck have 'special' component ids.
564+ return JpegColorSpace . Cmyk ;
512565 }
513566
514567 JpegThrowHelper . ThrowNotSupportedComponentCount ( componentCount ) ;
@@ -675,6 +728,8 @@ private void ExtendProfile(ref byte[] profile, byte[] extension)
675728 /// <param name="remaining">The remaining bytes in the segment block.</param>
676729 private void ProcessApplicationHeaderMarker ( BufferedReadStream stream , int remaining )
677730 {
731+ this . hasJFif = true ;
732+
678733 // We can only decode JFif identifiers.
679734 // Some images contain multiple JFIF markers (Issue 1932) so we check to see
680735 // if it's already been read.
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