limage - xcf/encoder.go

     1  package xcf
     2  
     3  import (
     4  	"image"
     5  	"image/color"
     6  	"io"
     7  
     8  	"vimagination.zapto.org/limage"
     9  	"vimagination.zapto.org/limage/lcolor"
    10  )
    11  
    12  const chanLen = 64 * 64 * 1 // tile width (64) * tile height (64) * max channels (4) * bytewidth (1)
    13  
    14  type colourBufFunc func(*encoder, color.Color)
    15  
    16  type encoder struct {
    17  	writer
    18  
    19  	colourPalette  lcolor.AlphaPalette
    20  	colourFunc     colourBufFunc
    21  	colourType     uint8
    22  	colourChannels uint8
    23  
    24  	channelBuf [4][chanLen]byte
    25  	colourBuf  [4]byte
    26  }
    27  
    28  // Encode encodes the given image as an XCF file to the given WriterAt
    29  func Encode(w io.WriterAt, im image.Image) error {
    30  	switch imt := im.(type) {
    31  	case *limage.Image:
    32  		im = *imt
    33  	case limage.Layer:
    34  		im = limage.Image{imt}
    35  	case *limage.Layer:
    36  		im = limage.Image{*imt}
    37  	}
    38  
    39  	e := encoder{
    40  		writer: newWriter(w),
    41  	}
    42  
    43  	e.Write(header)
    44  	b := im.Bounds()
    45  	e.WriteUint32(uint32(b.Dx()))
    46  	e.WriteUint32(uint32(b.Dy()))
    47  	switch cm := im.ColorModel(); cm {
    48  	case color.GrayModel, color.Gray16Model, lcolor.GrayAlphaModel:
    49  		e.colourType = 1
    50  		e.colourFunc = (*encoder).grayAlphaToBuf
    51  		e.colourChannels = 2
    52  	default:
    53  		switch m := cm.(type) {
    54  		case color.Palette:
    55  			e.colourPalette = lcolor.AlphaPalette(m)
    56  			e.colourType = 2
    57  			e.colourFunc = (*encoder).paletteAlphaToBuf
    58  			e.colourChannels = 2
    59  		case lcolor.AlphaPalette:
    60  			e.colourPalette = m
    61  			e.colourType = 2
    62  			e.colourFunc = (*encoder).paletteAlphaToBuf
    63  			e.colourChannels = 2
    64  		default:
    65  			e.colourType = 0
    66  			e.colourFunc = (*encoder).rgbAlphaToBuf
    67  			e.colourChannels = 4
    68  		}
    69  	}
    70  	e.WriteUint32(uint32(e.colourType))
    71  
    72  	// write property list
    73  
    74  	if e.colourPalette != nil {
    75  		e.WriteUint32(propColorMap)
    76  		e.WriteUint32(3*uint32(len(e.colourPalette)) + 4)
    77  		e.WriteUint32(uint32(len(e.colourPalette)))
    78  		for _, colour := range e.colourPalette {
    79  			rgb := lcolor.RGBModel.Convert(colour).(lcolor.RGB)
    80  			e.WriteUint8(rgb.R)
    81  			e.WriteUint8(rgb.G)
    82  			e.WriteUint8(rgb.B)
    83  		}
    84  	}
    85  
    86  	e.WriteUint32(propCompression)
    87  	e.WriteUint32(1)
    88  	e.WriteUint8(1) // rle
    89  
    90  	e.WriteUint32(0)
    91  	e.WriteUint32(0)
    92  
    93  	switch im := im.(type) {
    94  	case limage.Image:
    95  		pw := e.ReservePointerList(layerCount(im))
    96  		e.WriteUint32(0) // no channels
    97  		e.WriteLayers(im, 0, 0, make([]uint32, 0, 32), pw)
    98  	default:
    99  		pw := e.ReservePointerList(1)
   100  		e.WriteUint32(0) // no channels
   101  		e.WriteLayer(limage.Layer{Image: im}, 0, 0, []uint32{}, pw)
   102  	}
   103  
   104  	return e.Err
   105  }
   106  func layerCount(g limage.Image) uint32 {
   107  	count := uint32(len(g))
   108  	for _, l := range g {
   109  		switch g := l.Image.(type) {
   110  		case limage.Image:
   111  			count += layerCount(g)
   112  		case *limage.Image:
   113  			count += layerCount(*g)
   114  		}
   115  
   116  	}
   117  	return count
   118  }
   119  
   120  var header = []byte{'g', 'i', 'm', 'p', ' ', 'x', 'c', 'f', ' ', 'v', '0', '0', '3', 0}
   121