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