78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
package goeffects
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// Package copied from https://github.com/markdaws/go-effects
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import "image"
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import "runtime"
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// GSAlgo the type of algorithm to use when converting an image to it's grayscale equivalent
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type GSAlgo int
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const (
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// GSLIGHTNESS is the average of the min and max r,g,b value
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GSLIGHTNESS GSAlgo = iota
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// GSAVERAGE is the average of the r,g,b values of each pixel
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GSAVERAGE
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// GSLUMINOSITY used a weighting for r,g,b based on how the human eye perceives colors
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GSLUMINOSITY
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)
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type grayscale struct {
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algo GSAlgo
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}
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func (gs *grayscale) Apply(img *Image, numRoutines int) (*Image, error) {
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if numRoutines == 0 {
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numRoutines = runtime.GOMAXPROCS(0)
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}
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pf := func(ri, x, y, offset, inStride int, inPix, outPix []uint8) {
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var r, g, b uint8 = inPix[offset], inPix[offset+1], inPix[offset+2]
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switch gs.algo {
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case GSLIGHTNESS:
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maximum := float64(max(max(r, g), b))
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minimum := float64(max(min(r, g), b))
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r = uint8(maximum + minimum/2)
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g = r
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b = r
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case GSAVERAGE:
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r = (r + g + b) / 3
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g = r
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b = r
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case GSLUMINOSITY:
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r = uint8(0.21*float64(r) + 0.72*float64(g) + 0.07*float64(b))
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g = r
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b = r
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}
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outPix[offset] = r
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outPix[offset+1] = g
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outPix[offset+2] = b
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outPix[offset+3] = 255
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}
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out := &Image{
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img: image.NewRGBA(image.Rectangle{
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Min: image.Point{X: 0, Y: 0},
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Max: image.Point{X: img.Width, Y: img.Height},
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}),
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Width: img.Width,
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Height: img.Height,
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Bounds: Rect{
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X: img.Bounds.X,
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Y: img.Bounds.Y,
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Width: img.Bounds.Width,
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Height: img.Bounds.Height,
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},
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}
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runParallel(numRoutines, img, out.Bounds, out, pf, 0)
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return out, nil
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}
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// NewGrayscale renders the input image as a grayscale image. numRoutines specifies how many
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// goroutines should be used to process the image in parallel, use 0 to let the library decide
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func NewGrayscale(algo GSAlgo) Effect {
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return &grayscale{algo: algo}
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}
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