RosettaCodeData/Task/Bitmap/Go/bitmap-1.go

package main

import (
   "bytes"
   "fmt"
   "image"
   "image/color"
   "image/draw"
   "image/png"
)

func main() {
   // A rectangle from 0,0 to 300,240.
   r := image.Rect(0, 0, 300, 240)

   // Create an image
   im := image.NewNRGBA(r)

   // set some color variables for convience
   var (
      red  = color.RGBA{0xff, 0x00, 0x00, 0xff}
      blue = color.RGBA{0x00, 0x00, 0xff, 0xff}
   )

   // Fill with a uniform color
   draw.Draw(im, r, &image.Uniform{red}, image.ZP, draw.Src)

   // Set individual pixels
   im.Set(10, 20, blue)
   im.Set(20, 30, color.Black)
   im.Set(30, 40, color.RGBA{0x10, 0x20, 0x30, 0xff})

   // Get the values of specific pixels as color.Color types.
   // The color will be in the color.Model of the image (in this
   // case color.NRGBA) but color models can convert their values
   // to other models.
   c1 := im.At(0, 0)
   c2 := im.At(10, 20)

   // or directly as RGB components (scaled values)
   redc, greenc, bluec, _ := c1.RGBA()
   redc, greenc, bluec, _ = im.At(30, 40).RGBA()

   // Images can be read and writen in various formats
   var buf bytes.Buffer
   err := png.Encode(&buf, im)
   if err != nil {
      fmt.Println(err)
   }

   fmt.Println("Image size:", im.Bounds().Dx(), "×", im.Bounds().Dy())
   fmt.Println(buf.Len(), "bytes when encoded as PNG.")
   fmt.Printf("Pixel at %7v is %v\n", image.Pt(0, 0), c1)
   fmt.Printf("Pixel at %7v is %#v\n", image.Pt(10, 20), c2) // %#v shows type details
   fmt.Printf("Pixel at %7v has R=%d, G=%d, B=%d\n",
      image.Pt(30, 40), redc, greenc, bluec)
}