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package imaging
import (
"image"
"math"
)
// Anchor is the anchor point for image alignment.
type Anchor int
// Anchor point positions.
const (
Center Anchor = iota
TopLeft
Top
TopRight
Left
Right
BottomLeft
Bottom
BottomRight
)
func anchorPt(b image.Rectangle, w, h int, anchor Anchor) image.Point {
var x, y int
switch anchor {
case TopLeft:
x = b.Min.X
y = b.Min.Y
case Top:
x = b.Min.X + (b.Dx()-w)/2
y = b.Min.Y
case TopRight:
x = b.Max.X - w
y = b.Min.Y
case Left:
x = b.Min.X
y = b.Min.Y + (b.Dy()-h)/2
case Right:
x = b.Max.X - w
y = b.Min.Y + (b.Dy()-h)/2
case BottomLeft:
x = b.Min.X
y = b.Max.Y - h
case Bottom:
x = b.Min.X + (b.Dx()-w)/2
y = b.Max.Y - h
case BottomRight:
x = b.Max.X - w
y = b.Max.Y - h
default:
x = b.Min.X + (b.Dx()-w)/2
y = b.Min.Y + (b.Dy()-h)/2
}
return image.Pt(x, y)
}
// Crop cuts out a rectangular region with the specified bounds
// from the image and returns the cropped image.
func Crop(img image.Image, rect image.Rectangle) *image.NRGBA {
r := rect.Intersect(img.Bounds()).Sub(img.Bounds().Min)
if r.Empty() {
return &image.NRGBA{}
}
src := newScanner(img)
dst := image.NewNRGBA(image.Rect(0, 0, r.Dx(), r.Dy()))
rowSize := r.Dx() * 4
parallel(r.Min.Y, r.Max.Y, func(ys <-chan int) {
for y := range ys {
i := (y - r.Min.Y) * dst.Stride
src.scan(r.Min.X, y, r.Max.X, y+1, dst.Pix[i:i+rowSize])
}
})
return dst
}
// CropAnchor cuts out a rectangular region with the specified size
// from the image using the specified anchor point and returns the cropped image.
func CropAnchor(img image.Image, width, height int, anchor Anchor) *image.NRGBA {
srcBounds := img.Bounds()
pt := anchorPt(srcBounds, width, height, anchor)
r := image.Rect(0, 0, width, height).Add(pt)
b := srcBounds.Intersect(r)
return Crop(img, b)
}
// CropCenter cuts out a rectangular region with the specified size
// from the center of the image and returns the cropped image.
func CropCenter(img image.Image, width, height int) *image.NRGBA {
return CropAnchor(img, width, height, Center)
}
// Paste pastes the img image to the background image at the specified position and returns the combined image.
func Paste(background, img image.Image, pos image.Point) *image.NRGBA {
dst := Clone(background)
pos = pos.Sub(background.Bounds().Min)
pasteRect := image.Rectangle{Min: pos, Max: pos.Add(img.Bounds().Size())}
interRect := pasteRect.Intersect(dst.Bounds())
if interRect.Empty() {
return dst
}
src := newScanner(img)
parallel(interRect.Min.Y, interRect.Max.Y, func(ys <-chan int) {
for y := range ys {
x1 := interRect.Min.X - pasteRect.Min.X
x2 := interRect.Max.X - pasteRect.Min.X
y1 := y - pasteRect.Min.Y
y2 := y1 + 1
i1 := y*dst.Stride + interRect.Min.X*4
i2 := i1 + interRect.Dx()*4
src.scan(x1, y1, x2, y2, dst.Pix[i1:i2])
}
})
return dst
}
// PasteCenter pastes the img image to the center of the background image and returns the combined image.
func PasteCenter(background, img image.Image) *image.NRGBA {
bgBounds := background.Bounds()
bgW := bgBounds.Dx()
bgH := bgBounds.Dy()
bgMinX := bgBounds.Min.X
bgMinY := bgBounds.Min.Y
centerX := bgMinX + bgW/2
centerY := bgMinY + bgH/2
x0 := centerX - img.Bounds().Dx()/2
y0 := centerY - img.Bounds().Dy()/2
return Paste(background, img, image.Pt(x0, y0))
}
// Overlay draws the img image over the background image at given position
// and returns the combined image. Opacity parameter is the opacity of the img
// image layer, used to compose the images, it must be from 0.0 to 1.0.
//
// Usage examples:
//
// // Draw spriteImage over backgroundImage at the given position (x=50, y=50).
// dstImage := imaging.Overlay(backgroundImage, spriteImage, image.Pt(50, 50), 1.0)
//
// // Blend two opaque images of the same size.
// dstImage := imaging.Overlay(imageOne, imageTwo, image.Pt(0, 0), 0.5)
//
func Overlay(background, img image.Image, pos image.Point, opacity float64) *image.NRGBA {
opacity = math.Min(math.Max(opacity, 0.0), 1.0) // Ensure 0.0 <= opacity <= 1.0.
dst := Clone(background)
pos = pos.Sub(background.Bounds().Min)
pasteRect := image.Rectangle{Min: pos, Max: pos.Add(img.Bounds().Size())}
interRect := pasteRect.Intersect(dst.Bounds())
if interRect.Empty() {
return dst
}
src := newScanner(img)
parallel(interRect.Min.Y, interRect.Max.Y, func(ys <-chan int) {
scanLine := make([]uint8, interRect.Dx()*4)
for y := range ys {
x1 := interRect.Min.X - pasteRect.Min.X
x2 := interRect.Max.X - pasteRect.Min.X
y1 := y - pasteRect.Min.Y
y2 := y1 + 1
src.scan(x1, y1, x2, y2, scanLine)
i := y*dst.Stride + interRect.Min.X*4
j := 0
for x := interRect.Min.X; x < interRect.Max.X; x++ {
r1 := float64(dst.Pix[i+0])
g1 := float64(dst.Pix[i+1])
b1 := float64(dst.Pix[i+2])
a1 := float64(dst.Pix[i+3])
r2 := float64(scanLine[j+0])
g2 := float64(scanLine[j+1])
b2 := float64(scanLine[j+2])
a2 := float64(scanLine[j+3])
coef2 := opacity * a2 / 255
coef1 := (1 - coef2) * a1 / 255
coefSum := coef1 + coef2
coef1 /= coefSum
coef2 /= coefSum
dst.Pix[i+0] = uint8(r1*coef1 + r2*coef2)
dst.Pix[i+1] = uint8(g1*coef1 + g2*coef2)
dst.Pix[i+2] = uint8(b1*coef1 + b2*coef2)
dst.Pix[i+3] = uint8(math.Min(a1+a2*opacity*(255-a1)/255, 255))
i += 4
j += 4
}
}
})
return dst
}
// OverlayCenter overlays the img image to the center of the background image and
// returns the combined image. Opacity parameter is the opacity of the img
// image layer, used to compose the images, it must be from 0.0 to 1.0.
func OverlayCenter(background, img image.Image, opacity float64) *image.NRGBA {
bgBounds := background.Bounds()
bgW := bgBounds.Dx()
bgH := bgBounds.Dy()
bgMinX := bgBounds.Min.X
bgMinY := bgBounds.Min.Y
centerX := bgMinX + bgW/2
centerY := bgMinY + bgH/2
x0 := centerX - img.Bounds().Dx()/2
y0 := centerY - img.Bounds().Dy()/2
return Overlay(background, img, image.Point{x0, y0}, opacity)
}
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