limage - image.go

     1  package limage // import "vimagination.zapto.org/limage"
     2  
     3  import (
     4  	"image"
     5  	"image/color"
     6  
     7  	"vimagination.zapto.org/limage/internal"
     8  )
     9  
    10  // Image represents a collection of layers
    11  type Image []Layer
    12  
    13  // ColorModel represents the color model of the group. It uses the first layer
    14  // to determine the color model
    15  func (g Image) ColorModel() color.Model {
    16  	if len(g) == 0 {
    17  		return color.AlphaModel
    18  	}
    19  	return g[0].ColorModel()
    20  }
    21  
    22  // Bounds returns the limits for the dimensions of the group
    23  func (g Image) Bounds() image.Rectangle {
    24  	var r image.Rectangle
    25  	for _, l := range g {
    26  		r = r.Union(l.Bounds())
    27  	}
    28  	return r
    29  }
    30  
    31  // At returns the colour at the specified coords
    32  func (g Image) At(x, y int) color.Color {
    33  	c := color.Color(color.Alpha{})
    34  	point := image.Point{x, y}
    35  	for i := len(g) - 1; i >= 0; i-- {
    36  		if g[i].Invisible {
    37  			continue
    38  		}
    39  		if !point.In(g[i].Bounds()) {
    40  			continue
    41  		}
    42  		if _, ok := g.ColorModel().(color.Palette); g[i].Mode != CompositeDissolve && ok {
    43  			if d := internal.ColourToNRGBA(g[i].At(x, y)); d.A > 0x7fff {
    44  				d.A = 0xffff
    45  				c = d
    46  			}
    47  		} else {
    48  			c = g[i].Mode.Composite(c, g[i].At(x, y))
    49  		}
    50  	}
    51  	return c
    52  }
    53  
    54  // SubImage returns an image representing the portion of the image p visible
    55  // through r. The returned value shares pixels with the original image
    56  func (g Image) SubImage(r image.Rectangle) image.Image {
    57  	h := make(Image, len(g))
    58  	for n, l := range g {
    59  		h[n] = l.SubImageLayer(r)
    60  	}
    61  	return h
    62  }
    63