Wie positioniert und dreht man mehrere Bilder in Golang mit dem richtigen Z-Index?

package main

import (
    "fmt"
    "image"
    "image/draw"
    "image/jpeg"
    "code.google.com/p/graphics-go/graphics"
    "os"
)

func main() {
    // Load the background image
    fImg1, _ := os.Open("background.jpg")
    defer fImg1.Close()
    bi, _, _ := image.Decode(fImg1)

    // Load the overlay images
    fImg2, _ := os.Open("overlay1.jpg")
    defer fImg2.Close()
    i1, _, _ := image.Decode(fImg2)

    fImg3, _ := os.Open("overlay2.jpg")
    defer fImg3.Close()
    i2, _, _ := image.Decode(fImg3)

    // Create a new image to hold the final result
    m := image.NewRGBA(image.Rect(0, 0, bi.Bounds().Max.X, bi.Bounds().Max.Y))

    // Draw the background image
    draw.Draw(m, m.Bounds(), bi, image.Point{0, 0}, draw.Src)

    // Draw the overlay images with the specified positioning and rotation
    graphics.Rotate(m, i1, &graphics.RotateOptions{3.141592653589793, 0, 0})
    graphics.Draw(m, m.Bounds(), i2, image.Point{100, 100}, draw.Src)

    // Save the final image to a file
    toimg, _ := os.Create("new.jpg")
    defer toimg.Close()
    jpeg.Encode(toimg, m, &jpeg.Options{jpeg.DefaultQuality})

    fmt.Println("Image manipulation complete. Saved as 'new.jpg'.")
}