83 lines
2.0 KiB
Go
83 lines
2.0 KiB
Go
package images4
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import (
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"image"
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"image/color"
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_ "image/gif"
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"image/jpeg"
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"image/png"
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"log"
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"os"
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)
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// Open opens and decodes an image file for a given path.
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func Open(path string) (img image.Image, err error) {
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file, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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img, _, err = image.Decode(file)
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if err != nil {
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return nil, err
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}
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return img, err
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}
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// ResizeByNearest resizes an image to the destination size
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// with the nearest neighbour method. It also returns the source
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// image size.
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func ResizeByNearest(
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src image.Image, dstSize image.Point) (
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dst image.RGBA, srcSize image.Point) {
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// Original image size.
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xMax, xMin := src.Bounds().Max.X, src.Bounds().Min.X
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yMax, yMin := src.Bounds().Max.Y, src.Bounds().Min.Y
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srcX := xMax - xMin
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srcY := yMax - yMin
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xScale := float64(srcX) / float64(dstSize.X)
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yScale := float64(srcY) / float64(dstSize.Y)
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// Destination rectangle.
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outRect := image.Rectangle{
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image.Point{0, 0}, image.Point{dstSize.X, dstSize.Y}}
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// Color model of uint8 per color.
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dst = *image.NewRGBA(outRect)
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var (
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r, g, b, a uint32
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)
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for y := 0; y < dstSize.Y; y++ {
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for x := 0; x < dstSize.X; x++ {
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r, g, b, a = src.At(
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int(float64(x)*xScale)+xMin,
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int(float64(y)*yScale)+yMin).RGBA()
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dst.Set(x, y, color.RGBA{
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uint8(r >> 8),
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uint8(g >> 8),
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uint8(b >> 8),
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uint8(a >> 8)})
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}
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}
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return dst, image.Point{srcX, srcY}
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}
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// SaveToPNG encodes and saves image.RGBA to a file.
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func SaveToPNG(img *image.RGBA, path string) {
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if destFile, err := os.Create(path); err != nil {
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log.Println("Cannot create file: ", path, err)
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} else {
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defer destFile.Close()
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png.Encode(destFile, img)
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}
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}
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// SaveToJPG encodes and saves image.RGBA to a file.
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func SaveToJPG(img *image.RGBA, path string, quality int) {
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if destFile, err := os.Create(path); err != nil {
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log.Println("Cannot create file: ", path, err)
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} else {
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defer destFile.Close()
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jpeg.Encode(destFile, img, &jpeg.Options{Quality: quality})
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}
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}
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