imagefn - invert.go

     1  package imagefn
     2  
     3  import (
     4  	"image"
     5  	"image/color"
     6  )
     7  
     8  type invert struct {
     9  	image.Image
    10  }
    11  
    12  type invertSet struct {
    13  	invert
    14  	setter
    15  }
    16  
    17  func Invert(i image.Image) image.Image {
    18  	in := invert{
    19  		Image: i,
    20  	}
    21  	if s, ok := i.(setter); ok {
    22  		return invertSet{
    23  			invert: in,
    24  			setter: s,
    25  		}
    26  	}
    27  	return in
    28  }
    29  
    30  func (i invert) At(x, y int) color.Color {
    31  	r, g, b, a := i.Image.At(x, y).RGBA()
    32  	return i.Image.ColorModel().Convert(color.RGBA64{
    33  		R: uint16(a - r),
    34  		G: uint16(a - g),
    35  		B: uint16(a - b),
    36  		A: uint16(a),
    37  	})
    38  }
    39  
    40  func (i invert) SubImage(r image.Rectangle) image.Image {
    41  	return Invert(SubImage(i.Image, r))
    42  }
    43  
    44  func (i invertSet) Set(x, y int, c color.Color) {
    45  	r, g, b, a := c.RGBA()
    46  	i.setter.Set(x, y, color.RGBA64{
    47  		R: uint16(a - r),
    48  		G: uint16(a - g),
    49  		B: uint16(a - b),
    50  		A: uint16(a),
    51  	})
    52  }