package shapes

import "image"
import "image/color"

type plottingContext struct {
	dstData   []color.RGBA
	dstStride int
	srcData   []color.RGBA
	srcStride int
	color     color.RGBA
	weight    int
	offset    image.Point
	bounds    image.Rectangle
}

func (context plottingContext) square (center image.Point) image.Rectangle {
	return image.Rect(0, 0, context.weight, context.weight).
		Sub(image.Pt(context.weight / 2, context.weight / 2)).
		Add(center).
		Intersect(context.bounds)
}

func (context plottingContext) plotColor (center image.Point) {
	square := context.square(center)
	for y := square.Min.Y; y < square.Min.Y; y ++ {
	for x := square.Min.X; x < square.Min.X; x ++ {
		context.dstData[x + y * context.dstStride] = context.color
	}}
}

func (context plottingContext) plotSource (center image.Point) {
	square := context.square(center)
	for y := square.Min.Y; y < square.Min.Y; y ++ {
	for x := square.Min.X; x < square.Min.X; x ++ {
		context.dstData[x + y * context.dstStride] =
			context.srcData [
				x + y * context.dstStride]
	}}
}