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Allow read/write 16bit files #3

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Allow read/write 16bit files #3

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42 changes: 28 additions & 14 deletions reader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,13 @@
// per channel.
//
// To only be able to load pnm images using image.Decode, use
//
// import _ "github.com/jbuchbinder/gopnm"
//
// Not implemented are:
// - Writing pnm files in raw format.
// - Writing images with 16 bits per channel.
// - Writing images with a custom Maxvalue.
// - Reading/and writing PAM images.
// - Writing pnm files in raw format.
// - Reading/and writing PAM images.
//
// (I would be happy to accept patches for these.)
//
// Specifications can be found at http://netpbm.sourceforge.net/doc/#formats.
Expand Down Expand Up @@ -218,19 +218,33 @@ func decodeRawRGB(r io.Reader, c PNMConfig) (image.Image, error) {
}

func decodeRawRGB64(r io.Reader, c PNMConfig) (image.Image, error) {
m := image.NewRGBA(image.Rect(0, 0, c.Width, c.Height))
m := image.NewRGBA64(image.Rect(0, 0, c.Width, c.Height))
count := len(m.Pix)

for i := 0; i < count; i += 8 {
pixel := m.Pix[i : i+6]
m.Pix[i+6] = 0xff
m.Pix[i+7] = 0xff
if c.Maxval < 256 {
for i := 0; i+8 <= count; i += 8 {
pixel := m.Pix[i : i+6 : i+6]
m.Pix[i+6] = 0xff
m.Pix[i+7] = 0xff

if _, err := io.ReadFull(r, pixel); err != nil {
return nil, err
}
}
return m, nil
}

for i := 0; i+16 <= count; i += 16 {
pixel := m.Pix[i : i+12 : i+12]
m.Pix[i+12] = 0xff
m.Pix[i+13] = 0xff
m.Pix[i+14] = 0xff
m.Pix[i+15] = 0xff
if _, err := io.ReadFull(r, pixel); err != nil {
return nil, err
}
}

}
return m, nil
}

Expand All @@ -241,10 +255,10 @@ func decodePAM(r io.Reader, c PNMConfig) (image.Image, error) {
// Decode reads a PNM image from r and returns it as an image.Image.
//
// The type of Image returned depends on the PNM contents:
// - PBM: image.Gray with black = 0 and white = 255
// - PGM: image.Gray or image.Gray16, values as in the file
// - PPM: image.RGBA or image.RGBA64, values as in the file
// - PAM: not supported (yet)
// - PBM: image.Gray with black = 0 and white = 255
// - PGM: image.Gray or image.Gray16, values as in the file
// - PPM: image.RGBA or image.RGBA64, values as in the file
// - PAM: not supported (yet)
func Decode(r io.Reader) (image.Image, error) {
br := bufio.NewReader(r)
c, err := DecodeConfigPNM(br)
Expand Down
72 changes: 57 additions & 15 deletions writer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -91,11 +91,28 @@ func encodePGM(w io.Writer, m image.Image, maxvalue int) error {

// write raster
cm := color.GrayModel
row := make([]uint8, b.Dx())
setY := func(row []uint8, c color.Color, off int) {
row[off] = cm.Convert(c).(color.Gray).Y
}
var row []uint8
if maxvalue <= 255 {
row = make([]uint8, b.Dx())
} else {
cm = color.Gray16Model
row = make([]uint8, 2*b.Dx())
setY = func(row []uint8, cc color.Color, off int) {
// Each sample is represented in pure binary by either 1 or 2 bytes.
// If the Maxval is less than 256, it is 1 byte. Otherwise, it is 2 bytes.
// The most significant byte is first.
Y := cm.Convert(cc).(color.Gray16).Y
row[off*2] = uint8(Y >> 8)
row[off*2+1] = uint8(Y & 0xff)
}
}

for y := b.Min.Y; y < b.Max.Y; y++ {
for x := b.Min.X; x < b.Max.X; x++ {
c := cm.Convert(m.At(x, y)).(color.Gray)
row[x-b.Min.X] = c.Y
setY(row, m.At(x, y), x-b.Min.X)
}
if _, err := w.Write(row); err != nil {
return err
Expand All @@ -114,14 +131,32 @@ func encodePPM(w io.Writer, m image.Image, maxvalue int) error {

// write raster
cm := color.RGBAModel
row := make([]uint8, b.Dx()*3)
var row []uint8
set := func(row []uint8, cc color.Color, off int) {
c := cm.Convert(cc).(color.RGBA)
row[off] = c.R
row[off+1] = c.G
row[off+2] = c.B
}
if maxvalue <= 255 {
row = make([]uint8, b.Dx()*3)
} else {
cm = color.RGBA64Model
row = make([]uint8, b.Dx()*3*2)
set = func(row []uint8, cc color.Color, off int) {
c := cm.Convert(cc).(color.RGBA64)
row[off*2] = uint8(c.R >> 8)
row[off*2+1] = uint8(c.R & 0xff)
row[off*2+2] = uint8(c.G >> 8)
row[off*2+3] = uint8(c.G & 0xff)
row[off*2+4] = uint8(c.B >> 8)
row[off*2+5] = uint8(c.B & 0xff)
}
}
for y := b.Min.Y; y < b.Max.Y; y++ {
i := 0
for x := b.Min.X; x < b.Max.X; x++ {
c := cm.Convert(m.At(x, y)).(color.RGBA)
row[i] = c.R
row[i+1] = c.G
row[i+2] = c.B
set(row, m.At(x, y), i)
i += 3
}
if _, err := w.Write(row); err != nil {
Expand All @@ -134,20 +169,27 @@ func encodePPM(w io.Writer, m image.Image, maxvalue int) error {
// Encode writes an image.Image m to io.Writer w in PNM format.
//
// The specific format is determined by pnmType, this can be one of:
// - pnm.PBM (black/white)
// - pnm.PGM (grayscale)
// - pnm.PPM (RGB)
// - pnm.PBM (black/white)
// - pnm.PGM (grayscale)
// - pnm.PPM (RGB)
//
// The image m is converted if necessary.
// Note that PGM/PPM always use 8 bits per channel at the moment and that
// maxvalue is always 255.
func Encode(w io.Writer, m image.Image, pnmType int) error {
switch pnmType {
case PBM:
return encodePBM(w, m)
case PGM:
return encodePGM(w, m, 255)
maxint := 255
if m.ColorModel() == color.Gray16Model {
maxint = 65535
}
return encodePGM(w, m, maxint)
case PPM:
return encodePPM(w, m, 255)
maxint := 255
if m.ColorModel() == color.RGBA64Model {
maxint = 65535
}
return encodePPM(w, m, maxint)
}
return errors.New("Invalid PNM type specified.")
}