tomo-old/artist/patterns/texture.go

package patterns

import "image"
import "git.tebibyte.media/sashakoshka/tomo/canvas"

// Texture is a pattern that tiles the content of a canvas both horizontally and
// vertically.
type Texture struct {
	canvas.Canvas
}

// Draw tiles the pattern's canvas within the clipping bounds. The minimum
// points of the pattern's canvas and the destination canvas will be lined up.
func (pattern Texture) Draw (destination canvas.Canvas, clip image.Rectangle) {
	bounds := clip.Canon().Intersect(destination.Bounds())
	if bounds.Empty() { return }
	
	dstData, dstStride := destination.Buffer()
	srcData, srcStride := pattern.Buffer()
	srcBounds := pattern.Bounds()
	
	for y := bounds.Min.Y; y < bounds.Max.Y; y ++ {
	for x := bounds.Min.X; x < bounds.Max.X; x ++ {
		dstIndex := x + y * dstStride
		srcIndex :=
			wrap(x - bounds.Min.X, srcBounds.Min.X, srcBounds.Max.X) +
			wrap(x - bounds.Min.Y, srcBounds.Min.Y, srcBounds.Max.Y) * srcStride
		dstData[dstIndex] = srcData[srcIndex]
	}}
}

func wrap (value, min, max int) int {
	difference := max - min
	value = (value - min) % difference
	if value < 0 { value += difference }
	return value + min
}