ml
66 lines
1.6 KiB
Go
66 lines
1.6 KiB
Go
package bitmap
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import (
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"bytes"
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"image/color"
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"github.com/lucasb-eyer/go-colorful"
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)
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// RGB is describing Red, Green, and Blue intensities with 8-bit resolution.
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type RGB struct {
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Red uint8
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Green uint8
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Blue uint8
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}
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// Color returns the RGB data as a regular Color entry.
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func (col RGB) Color(alpha byte) color.Color {
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return color.RGBA{
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R: col.Red,
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G: col.Green,
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B: col.Blue,
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A: alpha,
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}
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}
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// PaletteSize indicates how many colors a palette can hold with a byte index.
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const PaletteSize = 256
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// Palette describes a list of colors to be used by bitmaps.
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// It is an array of 256 RGB values.
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type Palette [PaletteSize]RGB
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// ColorPalette returns a palette usable for the image packages.
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func (pal Palette) ColorPalette(firstIndexTransparent bool) color.Palette {
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result := make(color.Palette, len(pal))
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for index, col := range pal {
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alpha := byte(0xFF)
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if (index == 0) && firstIndexTransparent {
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alpha = 0x00
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}
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result[index] = col.Color(alpha)
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}
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return result
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}
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// IndexClosestTo returns the index into this palette that matches the given color the closest.
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// This search excludes the provided indices.
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func (pal Palette) IndexClosestTo(rgb RGB, excluding []byte) byte {
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targetColor, _ := colorful.MakeColor(rgb.Color(0xFF))
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closestDist := float64(-1)
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closestIndex := byte(0)
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for index, other := range pal {
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if bytes.IndexByte(excluding, byte(index)) >= 0 {
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continue
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}
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otherColor, _ := colorful.MakeColor(other.Color(0xFF))
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dist := targetColor.DistanceLab(otherColor)
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if (closestDist < 0) || (dist < closestDist) {
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closestDist = dist
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closestIndex = byte(index)
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}
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}
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return closestIndex
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}
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