imagefn - window.go

     1  package imagefn
     2  
     3  import (
     4  	"image"
     5  	"image/color"
     6  )
     7  
     8  type setter interface {
     9  	Set(int, int, color.Color)
    10  }
    11  
    12  type subimage interface {
    13  	SubImage(image.Rectangle) image.Image
    14  }
    15  
    16  func SubImage(i image.Image, r image.Rectangle) image.Image {
    17  	if si, ok := i.(subimage); ok {
    18  		return si.SubImage(r)
    19  	}
    20  	if s, ok := i.(setter); ok {
    21  		return &windowSet{
    22  			window: window{
    23  				Image:     i,
    24  				Rectangle: r,
    25  			},
    26  			setter: s,
    27  		}
    28  	}
    29  	return &window{
    30  		Image:     i,
    31  		Rectangle: r,
    32  	}
    33  }
    34  
    35  type window struct {
    36  	image.Image
    37  	Rectangle image.Rectangle
    38  }
    39  
    40  func (w *window) At(x, y int) color.Color {
    41  	if !image.Pt(x, y).In(w.Rectangle) {
    42  		return color.Transparent
    43  	}
    44  	return w.Image.At(x, y)
    45  }
    46  
    47  func (w *window) Bounds() image.Rectangle {
    48  	return w.Rectangle
    49  }
    50  
    51  func (w *window) SubImage(r image.Rectangle) image.Image {
    52  	r = r.Intersect(w.Rectangle)
    53  	return &window{
    54  		Image:     w.Image,
    55  		Rectangle: r,
    56  	}
    57  }
    58  
    59  type windowSet struct {
    60  	window
    61  	setter
    62  }
    63  
    64  func (w *windowSet) Set(x, y int, c color.Color) {
    65  	if !image.Pt(x, y).In(w.Rectangle) {
    66  		return
    67  	}
    68  	w.setter.Set(x, y, c)
    69  }