mirror of https://github.com/gohugoio/hugo
64 lines
1.8 KiB
Go
64 lines
1.8 KiB
Go
package images
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import (
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"fmt"
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"image"
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"image/color"
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"image/draw"
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"github.com/disintegration/gift"
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)
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// maskFilter applies a mask image to a base image.
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type maskFilter struct {
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mask ImageSource
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}
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// Draw applies the mask to the base image.
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func (f maskFilter) Draw(dst draw.Image, baseImage image.Image, options *gift.Options) {
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maskImage, err := f.mask.DecodeImage()
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if err != nil {
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panic(fmt.Sprintf("failed to decode image: %s", err))
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}
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// Ensure the mask is the same size as the base image
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baseBounds := baseImage.Bounds()
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maskBounds := maskImage.Bounds()
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// Resize mask to match base image size if necessary
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if maskBounds.Dx() != baseBounds.Dx() || maskBounds.Dy() != baseBounds.Dy() {
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g := gift.New(gift.Resize(baseBounds.Dx(), baseBounds.Dy(), gift.LanczosResampling))
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resizedMask := image.NewRGBA(g.Bounds(maskImage.Bounds()))
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g.Draw(resizedMask, maskImage)
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maskImage = resizedMask
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}
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// Use gift to convert the resized mask to grayscale
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g := gift.New(gift.Grayscale())
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grayscaleMask := image.NewGray(g.Bounds(maskImage.Bounds()))
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g.Draw(grayscaleMask, maskImage)
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// Convert grayscale mask to alpha mask
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alphaMask := image.NewAlpha(baseBounds)
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for y := baseBounds.Min.Y; y < baseBounds.Max.Y; y++ {
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for x := baseBounds.Min.X; x < baseBounds.Max.X; x++ {
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grayValue := grayscaleMask.GrayAt(x, y).Y
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alphaMask.SetAlpha(x, y, color.Alpha{A: grayValue})
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}
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}
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// Create an RGBA output image
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outputImage := image.NewRGBA(baseBounds)
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// Apply the mask using draw.DrawMask
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draw.DrawMask(outputImage, baseBounds, baseImage, image.Point{}, alphaMask, image.Point{}, draw.Over)
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// Copy the result to the destination
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gift.New().Draw(dst, outputImage)
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}
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// Bounds returns the bounds of the resulting image.
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func (f maskFilter) Bounds(imgBounds image.Rectangle) image.Rectangle {
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return image.Rect(0, 0, imgBounds.Dx(), imgBounds.Dy())
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}
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