76 lines
1.6 KiB
Go
76 lines
1.6 KiB
Go
package display
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import (
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"fmt"
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"github.com/egoist/mygo/ui"
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"rsc.io/qr"
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"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
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)
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type QRCodeOptions struct {
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// Scale is dots per module; zero means 2.
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Scale int
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}
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type qrKey struct{}
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type qrCache struct {
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text string
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code *qr.Code
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}
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// QRCode encodes s at level M, with a quiet zone.
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func QRCode(c *ui.Context, s string, o QRCodeOptions) *ui.Element {
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k := pixel.K(c)
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sc := pixel.Or("QRCode Scale", o.Scale, 2)
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e := ui.Box(c)
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qc := ui.Local(e, qrKey{}, func() qrCache { return qrCache{} })
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if qc.code == nil || qc.text != s {
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code, err := qr.Encode(s, qr.M)
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if err != nil {
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panic(fmt.Sprintf("display: QRCode %q: %v", s, err))
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}
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*qc = qrCache{s, code}
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}
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code := qc.code
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n := (code.Size + 8) * sc
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dark, light := extremes(k.Palette())
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return e.Size(k.D(n), k.D(n)).Role(ui.RoleImage).Label(s).Draw(func(p *ui.Painter, r ui.Rect) {
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g := k.Canvas(p, r)
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g.Rect(0, 0, n, n, light)
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for y := range code.Size {
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for x := 0; x < code.Size; {
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if !code.Black(x, y) {
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x++
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continue
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}
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end := x + 1
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for end < code.Size && code.Black(end, y) {
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end++
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}
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g.Rect((4+x)*sc, (4+y)*sc, (end-x)*sc, sc, dark)
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x = end
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}
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}
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})
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}
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// extremes are the darkest and lightest slots, for scanners.
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func extremes(pal *pixel.Palette) (dark, light pixel.Slot) {
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lum := func(s pixel.Slot) int {
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c := pal.Colors[s]
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return 299*int(c.R) + 587*int(c.G) + 114*int(c.B)
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}
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for s := range pixel.Slot(pixel.Slots) {
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if lum(s) < lum(dark) {
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dark = s
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}
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if lum(s) > lum(light) {
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light = s
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}
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}
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return dark, light
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}
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