Why not add interface about return the IM

[angelsmall]

hi, fogleman. Thank you very much for your open source project, but I found a problem.
I need a drawn 'image.Image' object and use GO's native method 'Jpeg. Encode' to convert the 'image.Image' object into an IO.Writer object,then I find that the 'context. DrawImage' method does not modify the 'image.Image' object passed in. I think you may be to ensure the security of the 'image.Image' object. However, I found that there was no function in the project to get the ‘context.im’ object, which caused me some trouble when I just wanted to get the image data for network transfer, not SaveJPG() on my disk. Perhaps adding a method to return the ‘context.im’ is more convenient and flexible to use.

// i use code
// This is a little demo that rotates a circular image
// the test.jpg not rotate
func defaultDrawCore(im image.Image) {
w := im.Bounds().Size().X
h := im.Bounds().Size().Y
dc := gg.NewContext(w, h)
dc.DrawRectangle(0, 0, float64(w), float64(h))
dc.SetRGBA(255, 255, 255, 0)
dc.Fill()
radius := math.Min(float64(w), float64(h)) / 2
dc.DrawCircle(float64(w/2), float64(h/2), radius)
dc.Clip()
dc.RotateAbout(gg.Radians(45), float64(w/2), float64(h/2))
dc.DrawImage(im, 0, 0)
buf := new(bytes.Buffer)
jpeg.Encode(buf, im, &jpeg.Options{Quality: 90})
newim, imErr := jpeg.Decode(buf)
if imErr != nil {
return
}
gg.SaveJPG("test.jpg", newim, 90)
return
}

// Perhaps adding a function will solve this problem
func (dc *Context) GetIM() *image.RGBA {
return dc.im
}