resize.go

package gfx

import (
	"image"
	"image/draw"
)

// NewResizedImage returns a new image with the provided dimensions.
func NewResizedImage(src image.Image, w, h int) image.Image {
	dst := NewImage(w, h)

	ResizeImage(dst, src)

	return dst
}

// NewScaledImage returns a new image scaled by the provided scaling factor.
func NewScaledImage(src image.Image, s float64) image.Image {
	b := src.Bounds()

	if b.Empty() {
		return &image.RGBA{}
	}

	return NewResizedImage(src, int(float64(b.Dx())*s), int(float64(b.Dy())*s))
}

// NewResizedRGBA returns a new RGBA image with the provided dimensions.
func NewResizedRGBA(src image.Image, r image.Rectangle) *image.RGBA {
	dst := NewRGBA(r)

	ResizeImage(dst, src)

	return dst
}

// NewScaledRGBA returns a new RGBA image scaled by the provided scaling factor.
func NewScaledRGBA(src image.Image, s float64) *image.RGBA {
	b := src.Bounds()

	if b.Empty() {
		return &image.RGBA{}
	}

	return NewResizedRGBA(src, IR(0, 0, int(float64(b.Dx())*s), int(float64(b.Dy())*s)))
}

// ResizeImage using nearest neighbor scaling on dst from src.
func ResizeImage(dst draw.Image, src image.Image) {
	w := dst.Bounds().Dx()
	h := dst.Bounds().Dy()

	xRatio := src.Bounds().Dx()<<16/w + 1
	yRatio := src.Bounds().Dy()<<16/h + 1

	for x := 0; x < w; x++ {
		for y := 0; y < h; y++ {
			sx := ((x * xRatio) >> 16)
			sy := ((y * yRatio) >> 16)

			dst.Set(x, y, src.At(sx, sy))
		}
	}
}