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tomo-old/artist/patterns/texture.go

78 lines
2.2 KiB
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 given bounds. The minimum
// point of the pattern's canvas will be lined up with the minimum point of the
// bounding rectangle.
func (pattern Texture) Draw (destination canvas.Canvas, bounds image.Rectangle) {
dstBounds := bounds.Canon().Intersect(destination.Bounds())
if dstBounds.Empty() { return }
dstData, dstStride := destination.Buffer()
srcData, srcStride := pattern.Buffer()
srcBounds := pattern.Bounds()
// offset is a vector that is added to points in destination space to
// convert them to points in source space
offset := srcBounds.Min.Sub(bounds.Min)
// calculate the starting position in source space
srcPoint := dstBounds.Min.Add(offset)
srcPoint.X = wrap(srcPoint.X, srcBounds.Min.X, srcBounds.Max.X)
srcPoint.Y = wrap(srcPoint.Y, srcBounds.Min.Y, srcBounds.Max.Y)
srcStartPoint := srcPoint
// for each row
dstPoint := image.Point { }
for dstPoint.Y = dstBounds.Min.Y; dstPoint.Y < dstBounds.Max.Y; dstPoint.Y ++ {
srcPoint.X = srcStartPoint.X
dstPoint.X = dstBounds.Min.X
dstYComponent := dstPoint.Y * dstStride
srcYComponent := srcPoint.Y * srcStride
// for each pixel in the row
for {
// draw pixel
dstIndex := dstYComponent + dstPoint.X
srcIndex := srcYComponent + srcPoint.X
dstData[dstIndex] = srcData[srcIndex]
// increment X in source space. wrap to start if out of
// bounds.
srcPoint.X ++
if srcPoint.X >= srcBounds.Max.X {
srcPoint.X = srcBounds.Min.X
}
// increment X in destination space. stop drawing this
// row if out of bounds.
dstPoint.X ++
if dstPoint.X >= dstBounds.Max.X {
break
}
}
// increment row in source space. wrap to start if out of
// bounds.
srcPoint.Y ++
if srcPoint.Y >= srcBounds.Max.Y {
srcPoint.Y = srcBounds.Min.Y
}
}
}
func wrap (value, min, max int) int {
difference := max - min
value = (value - min) % difference
if value < 0 { value += difference }
return value + min
}