Created an Image type.
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299a2b9c9d
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164
image.go
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164
image.go
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package oklab
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import (
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"encoding/binary"
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"image"
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"image/color"
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"image/draw"
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"math"
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)
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// Not many images can say they have 256-bit color;
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// I've definitely gone overboard with this.
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const bytesPerPixel = 8 * 4
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// Image represents an image that encodes its pixels using OKLab color.
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//
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// Each pixel is 32 bytes in size, encoding the Lightness, ChromaA, ChromaB, and Alpha components
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// of each pixel in that order as big-endian float64 values.
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type Image struct {
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Pix []uint8
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Stride int
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Rect image.Rectangle
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}
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// ColorModel implements the [image.Image] interface.
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func (p *Image) ColorModel() color.Model {
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return Model
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}
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// Bounds implements the [image.Image] interface.
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func (p *Image) Bounds() image.Rectangle {
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return p.Rect
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}
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// At implements the [image.Image] interface.
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func (p *Image) At(x, y int) color.Color {
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return p.OkLabAt(x, y)
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}
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// RGBA64At implements the [image.RGBA64Image] interface.
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func (p *Image) RGBA64At(x, y int) color.RGBA64 {
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r, g, b, a := p.OkLabAt(x, y).RGBA()
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return color.RGBA64{uint16(r), uint16(g), uint16(b), uint16(a)}
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}
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// OkLabAt decodes the pixel at the given coordinates into an OkLab color.
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//
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// The zero value is returned for coordinates outside of the image.
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func (p *Image) OkLabAt(x, y int) Color {
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if !image.Pt(x, y).In(p.Rect) {
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return Color{}
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}
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i := p.PixOffset(x, y)
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in := p.Pix[i : i+bytesPerPixel]
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return Color{
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Lightness: math.Float64frombits(binary.BigEndian.Uint64(in[0:8])),
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ChromaA: math.Float64frombits(binary.BigEndian.Uint64(in[8:16])),
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ChromaB: math.Float64frombits(binary.BigEndian.Uint64(in[16:24])),
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A: math.Float64frombits(binary.BigEndian.Uint64(in[24:32])),
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}
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}
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// PixOffset returns the offset into the [Pix] slice a pixel begins.
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//
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// The given coordinates must be inside the image.
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func (p *Image) PixOffset(x, y int) int {
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return (y-p.Rect.Min.Y)*p.Stride + (x-p.Rect.Min.X)*bytesPerPixel
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}
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// Set implements the [draw.Image] interface.
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func (p *Image) Set(x, y int, c color.Color) {
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if !image.Pt(x, y).In(p.Rect) {
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return
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}
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p.setOkLab(x, y, FromColor(c))
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}
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// Set implements the [draw.RGBA64Image] interface.
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func (p *Image) SetRGBA64(x, y int, c color.RGBA64) {
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if !image.Pt(x, y).In(p.Rect) {
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return
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}
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p.setOkLab(x, y, FromRGBA(uint32(c.R), uint32(c.G), uint32(c.B), uint32(c.A)))
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}
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func (p *Image) setOkLab(x, y int, c Color) {
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i := p.PixOffset(x, y)
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out := p.Pix[i : i+bytesPerPixel]
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binary.BigEndian.PutUint64(out[0:8], math.Float64bits(c.Lightness))
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binary.BigEndian.PutUint64(out[8:16], math.Float64bits(c.ChromaA))
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binary.BigEndian.PutUint64(out[16:24], math.Float64bits(c.ChromaB))
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binary.BigEndian.PutUint64(out[24:32], math.Float64bits(c.A))
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}
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// SetOkLab encodes the given color into the pixel at the given coordinates.
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//
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// Does nothing if the coordinates are outside the image.
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func (p *Image) SetOkLab(x, y int, c Color) {
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if !image.Pt(x, y).In(p.Rect) {
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return
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}
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p.setOkLab(x, y, c)
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}
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// SubImage returns a new [Image] that shares the same underlying pixel data.
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func (p *Image) SubImage(r image.Rectangle) *Image {
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r = r.Intersect(p.Rect)
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if r.Empty() {
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return &Image{}
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}
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start := p.PixOffset(r.Min.X, r.Min.Y)
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end := p.PixOffset(r.Max.X-1, r.Max.Y-1) + bytesPerPixel
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return &Image{
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Pix: p.Pix[start:end:end],
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Stride: p.Stride,
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Rect: r,
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}
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}
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// Opaque returns true if every pixel in the image would have an alpha value of 0xffff when
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// converted to [color.RGBA64].
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func (p *Image) Opaque() bool {
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w, h := p.Rect.Dx(), p.Rect.Dy()
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for y := 0; y < h; y++ {
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row := p.Pix[y*p.Stride : y*p.Stride+w*bytesPerPixel]
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for i, stop := 0, w*bytesPerPixel; i < stop; i += bytesPerPixel {
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// we consider a pixel opaque if the NRGBA/RGBA methods
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// would have returned 0xffff.
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if uint32(math.Float64frombits(binary.BigEndian.Uint64(row[i+24:i+32]))*0xffff+0.5) != 0xffff {
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return false
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}
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}
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}
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return true
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}
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// NewImage returns a new [Image] of the specified size.
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func NewImage(r image.Rectangle) *Image {
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return &Image{
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Pix: make([]uint8, r.Dx()*r.Dy()*bytesPerPixel),
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Stride: r.Dx() * bytesPerPixel,
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Rect: r,
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}
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}
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var (
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// type assertions
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_ interface {
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image.Image
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draw.Image
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image.RGBA64Image
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draw.RGBA64Image
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} = (*Image)(nil)
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)
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245
image_test.go
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245
image_test.go
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package oklab
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import (
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"image"
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"image/color"
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"image/draw"
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"testing"
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)
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func TestNewImage(t *testing.T) {
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r := image.Rect(13, 21, 34, 55)
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img := NewImage(r)
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if img.Rect != r {
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t.Errorf("img.Rect = %v, want %v", img.Rect, r)
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}
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if got := img.Bounds(); got != r {
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t.Errorf("img.Bounds() = %v, want %v", got, r)
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}
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if got := img.ColorModel(); got != Model {
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t.Errorf("img.ColorModel() = %v, want %v", got, Model)
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}
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if got, want := img.Stride, r.Dx()*bytesPerPixel; got != want {
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t.Errorf("img.Stride = %v, want %v", got, want)
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}
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if got, want := len(img.Pix), (r.Dy()-1)*img.Stride+r.Dx()*bytesPerPixel; got != want {
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t.Errorf("len(img.Pix) = %v, want %v", got, want)
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}
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}
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func testColor(x, y int) Color {
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return Color{
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float64(x),
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float64(y),
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float64(x + y),
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float64(x ^ y),
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}
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}
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func mod(a int, m int) int {
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a = a % m
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if a < 0 {
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// fucking intel.
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a += m
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}
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return a
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}
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func testRGBA64Color(x, y int) color.RGBA64 {
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a := mod(x^y, 0xffff)
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return color.RGBA64{
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uint16(mod(x, a+1)),
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uint16(mod(y, a+1)),
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uint16(mod(x+y, a+1)),
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uint16(a),
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}
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}
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func TestImage_Set(t *testing.T) {
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r := image.Rect(13, 21, 34, 55)
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img := NewImage(r)
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// intentionally invoking SetOkLab beyond the boundaries of the image, here.
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for y := r.Min.Y - 1; y <= r.Max.Y; y++ {
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for x := r.Min.X - 1; x <= r.Max.X; x++ {
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img.Set(x, y, testColor(x, y))
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}
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}
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for y := r.Min.Y - 1; y <= r.Max.Y; y++ {
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for x := r.Min.X - 1; x <= r.Max.X; x++ {
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want := Color{}
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if image.Pt(x, y).In(r) {
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want = testColor(x, y)
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}
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got := img.At(x, y).(Color)
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if got != want {
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t.Errorf("img.At(%d, %d) = %v, want %v", x, y, got, want)
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// stop at the first error, please.
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return
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}
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}
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}
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}
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func TestImage_SetRGBA64(t *testing.T) {
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r := image.Rect(13, 21, 34, 55)
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img := NewImage(r)
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// intentionally invoking SetOkLab beyond the boundaries of the image, here.
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for y := r.Min.Y - 1; y <= r.Max.Y; y++ {
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for x := r.Min.X - 1; x <= r.Max.X; x++ {
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img.SetRGBA64(x, y, testRGBA64Color(x, y))
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}
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}
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for y := r.Min.Y - 1; y <= r.Max.Y; y++ {
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for x := r.Min.X - 1; x <= r.Max.X; x++ {
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want := color.RGBA64{}
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if image.Pt(x, y).In(r) {
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want = testRGBA64Color(x, y)
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}
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got := img.RGBA64At(x, y)
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if got != want {
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t.Errorf("img.RGBA64At(%d, %d) = %v, want %v", x, y, got, want)
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// stop at the first error, please.
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return
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}
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}
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}
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}
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func setPixels(img *Image) {
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for y := img.Rect.Min.Y - 1; y <= img.Rect.Max.Y; y++ {
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for x := img.Rect.Min.X - 1; x <= img.Rect.Max.X; x++ {
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img.SetOkLab(x, y, testColor(x, y))
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}
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}
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}
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func checkPixels(t *testing.T, img *Image) {
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for y := img.Rect.Min.Y - 1; y <= img.Rect.Max.Y; y++ {
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for x := img.Rect.Min.X - 1; x <= img.Rect.Max.X; x++ {
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want := Color{}
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if image.Pt(x, y).In(img.Rect) {
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want = testColor(x, y)
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}
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got := img.OkLabAt(x, y)
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if got != want {
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t.Errorf("checkPixels: img.OkLabAt(%d, %d) = %v, want %v", x, y, got, want)
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return
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}
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}
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}
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}
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func TestImage_SetOkLab(t *testing.T) {
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r := image.Rect(13, 21, 34, 55)
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img := NewImage(r)
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setPixels(img)
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checkPixels(t, img)
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}
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func TestImage_SubImage(t *testing.T) {
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r := image.Rect(13, 21, 34, 55)
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img := NewImage(r)
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setPixels(img)
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for _, tt := range []struct {
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name string
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r image.Rectangle
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}{
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{"identity", r},
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{"inset", r.Inset(1)},
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{"outset", r.Inset(-1)},
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{"left", r.Add(image.Pt(-1, 0))},
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{"right", r.Add(image.Pt(1, 0))},
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{"up", r.Add(image.Pt(0, -1))},
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{"down", r.Add(image.Pt(0, 1))},
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{"outside", image.Rect(-100, -100, 1, 1)},
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} {
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t.Run(tt.name, func(t *testing.T) {
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subImage := img.SubImage(tt.r)
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if got, want := subImage.Rect, img.Rect.Intersect(tt.r); got != want {
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t.Errorf("subImage.Rect = %v, want %v", got, want)
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return
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}
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if got, want := subImage.Stride, subImage.Rect.Dx()*bytesPerPixel; got < want {
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t.Errorf("subImage.Stride = %v, want >= %v", got, want)
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}
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if got, want := len(subImage.Pix), (subImage.Rect.Dy()-1)*subImage.Stride+subImage.Rect.Dx()*bytesPerPixel; got != want {
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t.Errorf("len(img.Pix) = %v, want %v", got, want)
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}
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checkPixels(t, subImage)
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})
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}
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}
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func TestImage_Opaque(t *testing.T) {
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t.Run("empty", func(t *testing.T) {
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// an empty image is opaque by virtue of not containing any pixels, opaque or otherwise.
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got, want := NewImage(image.Rect(0, 0, 0, 0)).Opaque(), true
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if got != want {
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t.Errorf("Opaque() = %v, want %v", got, want)
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}
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})
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t.Run("non-empty", func(t *testing.T) {
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img := NewImage(image.Rect(13, 21, 34, 55))
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// the pixels of a non-empty image will have an alpha value of zero,
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// make it completely transparent.
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got, want := img.Opaque(), false
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if got != want {
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t.Errorf("img.Opaque() = %v, want %v", got, want)
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}
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t.Run("explicitly transparent", func(t *testing.T) {
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// if we explicitly set every pixel to be transparent, the result should be the same.
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draw.Draw(img, img.Rect, image.Transparent, image.Point{}, draw.Src)
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got, want := img.Opaque(), false
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if got != want {
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t.Errorf("img.Opaque() = %v, want %v", got, want)
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}
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})
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t.Run("opaque", func(t *testing.T) {
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// make every pixel opaque.
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draw.Draw(img, img.Rect, image.Opaque, image.Point{}, draw.Src)
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got, want := img.Opaque(), true
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if got != want {
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t.Errorf("img.Opaque() = %v, want %v", got, want)
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}
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t.Run("except for a single transparent pixel", func(t *testing.T) {
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img.Set(14, 23, color.Transparent)
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got, want := img.Opaque(), false
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if got != want {
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t.Errorf("img.Opaque() = %v, want %v", got, want)
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}
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})
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})
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})
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}
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