Golang绘图技术（image/draw包介绍）

   1: // Draw calls DrawMask with a nil mask.

   2: func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op)

   3: func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point,

   4:     mask image.Image, mp image.Point, op Op)

   1: m := image.NewRGBA(image.Rect(0, 0, 640, 480))

   2: blue := color.RGBA{0, 0, 255, 255}

   3: draw.Draw(m, m.Bounds(), &image.Uniform{blue}, image.ZP, draw.Src)

   1: r := image.Rectangle{dp, dp.Add(sr.Size())}  // 获得更换区域

   2: draw.Draw(dst, r, src, sr.Min, draw.Src)

   1: sr = src.Bounds()         // 获取要复制图片的尺寸

   2: r := sr.Sub(sr.Min).Add(dp)   // 目标图的要剪切区域

   3: draw.Draw(dst, r, src, sr.Min, draw.Src)

   1: b := m.Bounds()

   2: p := image.Pt(0, 20)

   3: // Note that even though the second argument is b,

   4: // the effective rectangle is smaller due to clipping.

   5: draw.Draw(m, b, m, b.Min.Add(p), draw.Src)

   6: dirtyRect := b.Intersect(image.Rect(b.Min.X, b.Max.Y-20, b.Max.X, b.Max.Y))

   1: b := src.Bounds()

   2: m := image.NewRGBA(b)

   3: draw.Draw(m, b, src, b.Min, draw.Src)

   1: type circle struct {

   2:     p image.Point

   3:     r int

   4: }

   5:  

   6: func (c *circle) ColorModel() color.Model {

   7:     return color.AlphaModel

   8: }

   9:  

  10: func (c *circle) Bounds() image.Rectangle {

  11:     return image.Rect(c.p.X-c.r, c.p.Y-c.r, c.p.X+c.r, c.p.Y+c.r)

  12: }

  13:  

  14: func (c *circle) At(x, y int) color.Color {

  15:     xx, yy, rr := float64(x-c.p.X)+0.5, float64(y-c.p.Y)+0.5, float64(c.r)

  16:     if xx*xx+yy*yy  
   
  
  17:         return color.Alpha{255}
 
   
  
  18:     }
 
   
  
  19:     return color.Alpha{0}
 
   
  
  20: }
 
   
  
  21:  
 
   
  
  22:  
 
   
  
  23: draw.DrawMask(dst, dst.Bounds(), src, image.ZP, &circle{p, r}, image.ZP, draw.Over)
 
   
 

   1: type Image interface {

   2:     // ColorModel returns the Image's color model.

   3:     ColorModel() color.Model

   4:     // Bounds returns the domain for which At can return non-zero color.

   5:     // The bounds do not necessarily contain the point (0, 0).

   6:     Bounds() Rectangle

   7:     // At returns the color of the pixel at (x, y).

   8:     // At(Bounds().Min.X, Bounds().Min.Y) returns the upper-left pixel of the grid.

   9:     // At(Bounds().Max.X-1, Bounds().Max.Y-1) returns the lower-right one.

  10:     At(x, y int) color.Color

  11: }

   1: src := &image.Uniform{color.RGBA{0, 0, 255, 255}}

   2: mask := theGlyphImageForAFont()

   3: mr := theBoundsFor(glyphIndex)

   4: draw.DrawMask(dst, mr.Sub(mr.Min).Add(p), src, image.ZP, mask, mr.Min, draw.Over)