package main

import (
    "image"
    "image/color"
    "image/draw"
    "image/png"
    "os"
)

func main() {
    // Create a 320 x 240 image
    img := image.NewRGBA(image.Rect(0, 0, 320, 240))
    // fill img in white
    draw.Draw(img, img.Bounds(), &image.Uniform{color.RGBA{0, 0, 0, 0}}, image.ZP, draw.Src)
    // Draw a red dot at (100, 100)
    img.Set(100, 100, color.RGBA{255, 0, 0, 255})
    // Save to new.png
    w, _ := os.OpenFile("new.png", os.O_WRONLY|os.O_CREATE, 0600)
    defer w.Close()
    png.Encode(w, img)
}