image/jpeg: support RGB JPEG images.

The testdata was generated by:
convert video-001.png tmp1.tga
cjpeg -rgb -sample 2x2,1x1,1x1 tmp1.tga > video-001.rgb.jpeg
djpeg -nosmooth -targa video-001.rgb.jpeg > tmp2.tga
convert tmp2.tga video-001.rgb.png
rm tmp1.tga tmp2.tga

Change-Id: I5da0591b9005c1c75e807311f157d385e0e20a38
Reviewed-on: https://go-review.googlesource.com/6910
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/image/decode_test.go b/src/image/decode_test.go
index e88bfdaaaea241a28adb64adb936b6ece38e0f93..8b0b6e84b0f406d3f3157bf31a6c2da1e81abf3d 100644 (file)
--- a/src/image/decode_test.go
+++ b/src/image/decode_test.go
@@ -33,6 +33,7 @@ var imageTests = []imageTest{
        {"testdata/video-001.png", "testdata/video-001.jpeg", 8 << 8},
        {"testdata/video-001.png", "testdata/video-001.progressive.jpeg", 8 << 8},
        {"testdata/video-001.cmyk.png", "testdata/video-001.cmyk.jpeg", 8 << 8},
+       {"testdata/video-001.rgb.png", "testdata/video-001.rgb.jpeg", 8 << 8},
        // Grayscale images.
        {"testdata/video-005.gray.png", "testdata/video-005.gray.jpeg", 8 << 8},
        {"testdata/video-005.gray.png", "testdata/video-005.gray.png", 0},

diff --git a/src/image/jpeg/reader.go b/src/image/jpeg/reader.go
index 994c42232e06b1c6b411d5cdc416bfb406faec4b..7293f4561797e2f96e737f311c63563d15fe844f 100644 (file)
--- a/src/image/jpeg/reader.go
+++ b/src/image/jpeg/reader.go
@@ -126,6 +126,7 @@ type decoder struct {
        ri                  int // Restart Interval.
        nComp               int
        progressive         bool
+       jfif                bool
        adobeTransformValid bool
        adobeTransform      uint8
        eobRun              uint16 // End-of-Band run, specified in section G.1.2.2.
@@ -297,7 +298,7 @@ func (d *decoder) processSOF(n int) error {
        switch n {
        case 6 + 3*1: // Grayscale image.
                d.nComp = 1
-       case 6 + 3*3: // YCbCr image. (TODO(nigeltao): or RGB image.)
+       case 6 + 3*3: // YCbCr or RGB image.
                d.nComp = 3
        case 6 + 3*4: // YCbCrK or CMYK image.
                d.nComp = 4
@@ -448,6 +449,23 @@ func (d *decoder) processDRI(n int) error {
        return nil
 }
 
+func (d *decoder) processApp0Marker(n int) error {
+       if n < 5 {
+               return d.ignore(n)
+       }
+       if err := d.readFull(d.tmp[:5]); err != nil {
+               return err
+       }
+       n -= 5
+
+       d.jfif = d.tmp[0] == 'J' && d.tmp[1] == 'F' && d.tmp[2] == 'I' && d.tmp[3] == 'F' && d.tmp[4] == '\x00'
+
+       if n > 0 {
+               return d.ignore(n)
+       }
+       return nil
+}
+
 func (d *decoder) processApp14Marker(n int) error {
        if n < 12 {
                return d.ignore(n)
@@ -553,17 +571,34 @@ func (d *decoder) decode(r io.Reader, configOnly bool) (image.Image, error) {
                case sof0Marker, sof1Marker, sof2Marker:
                        d.progressive = marker == sof2Marker
                        err = d.processSOF(n)
-                       if configOnly {
+                       if configOnly && d.jfif {
                                return nil, err
                        }
                case dhtMarker:
-                       err = d.processDHT(n)
+                       if configOnly {
+                               err = d.ignore(n)
+                       } else {
+                               err = d.processDHT(n)
+                       }
                case dqtMarker:
-                       err = d.processDQT(n)
+                       if configOnly {
+                               err = d.ignore(n)
+                       } else {
+                               err = d.processDQT(n)
+                       }
                case sosMarker:
+                       if configOnly {
+                               return nil, nil
+                       }
                        err = d.processSOS(n)
                case driMarker:
-                       err = d.processDRI(n)
+                       if configOnly {
+                               err = d.ignore(n)
+                       } else {
+                               err = d.processDRI(n)
+                       }
+               case app0Marker:
+                       err = d.processApp0Marker(n)
                case app14Marker:
                        err = d.processApp14Marker(n)
                default:
@@ -585,6 +620,8 @@ func (d *decoder) decode(r io.Reader, configOnly bool) (image.Image, error) {
        if d.img3 != nil {
                if d.blackPix != nil {
                        return d.applyBlack()
+               } else if d.isRGB() {
+                       return d.convertToRGB()
                }
                return d.img3, nil
        }
@@ -663,6 +700,36 @@ func (d *decoder) applyBlack() (image.Image, error) {
        return img, nil
 }
 
+func (d *decoder) isRGB() bool {
+       if d.jfif {
+               return false
+       }
+       if d.adobeTransformValid && d.adobeTransform == adobeTransformUnknown {
+               // http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe
+               // says that 0 means Unknown (and in practice RGB) and 1 means YCbCr.
+               return true
+       }
+       return d.comp[0].c == 'R' && d.comp[1].c == 'G' && d.comp[2].c == 'B'
+}
+
+func (d *decoder) convertToRGB() (image.Image, error) {
+       cScale := d.comp[0].h / d.comp[1].h
+       bounds := d.img3.Bounds()
+       img := image.NewRGBA(bounds)
+       for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+               po := img.PixOffset(bounds.Min.X, y)
+               yo := d.img3.YOffset(bounds.Min.X, y)
+               co := d.img3.COffset(bounds.Min.X, y)
+               for i, iMax := 0, bounds.Max.X-bounds.Min.X; i < iMax; i++ {
+                       img.Pix[po+4*i+0] = d.img3.Y[yo+i]
+                       img.Pix[po+4*i+1] = d.img3.Cb[co+i/cScale]
+                       img.Pix[po+4*i+2] = d.img3.Cr[co+i/cScale]
+                       img.Pix[po+4*i+3] = 255
+               }
+       }
+       return img, nil
+}
+
 // drawYCbCr is the non-exported drawYCbCr function copy/pasted from the
 // image/draw package. It is copy/pasted because it doesn't seem right for the
 // image/jpeg package to depend on image/draw.
@@ -760,8 +827,12 @@ func DecodeConfig(r io.Reader) (image.Config, error) {
                        Height:     d.height,
                }, nil
        case 3:
+               cm := color.YCbCrModel
+               if d.isRGB() {
+                       cm = color.RGBAModel
+               }
                return image.Config{
-                       ColorModel: color.YCbCrModel, // TODO(nigeltao): support RGB JPEGs.
+                       ColorModel: cm,
                        Width:      d.width,
                        Height:     d.height,
                }, nil

diff --git a/src/image/testdata/video-001.rgb.jpeg b/src/image/testdata/video-001.rgb.jpeg
new file mode 100644 (file)
index 0000000..fc2ce3c
Binary files /dev/null and b/src/image/testdata/video-001.rgb.jpeg differ

diff --git a/src/image/testdata/video-001.rgb.png b/src/image/testdata/video-001.rgb.png
new file mode 100644 (file)
index 0000000..edb716d
Binary files /dev/null and b/src/image/testdata/video-001.rgb.png differ