43 lines
1.1 KiB
Go
43 lines
1.1 KiB
Go
package canvas
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import (
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"image"
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"math"
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"github.com/tfriedel6/canvas/backend/backendbase"
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)
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func (cv *Canvas) drawShadow(pts [][2]float64, mask *image.Alpha, canOverlap bool) {
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if cv.state.shadowColor.A == 0 {
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return
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}
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if cv.state.shadowOffsetX == 0 && cv.state.shadowOffsetY == 0 {
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return
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}
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if cv.shadowBuf == nil || cap(cv.shadowBuf) < len(pts) {
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cv.shadowBuf = make([][2]float64, 0, len(pts)+1000)
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}
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cv.shadowBuf = cv.shadowBuf[:0]
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for _, pt := range pts {
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cv.shadowBuf = append(cv.shadowBuf, [2]float64{
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pt[0] + cv.state.shadowOffsetX,
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pt[1] + cv.state.shadowOffsetY,
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})
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}
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color := cv.state.shadowColor
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color.A = uint8(math.Round(((float64(color.A) / 255.0) * cv.state.globalAlpha) * 255.0))
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style := backendbase.FillStyle{Color: color, Blur: cv.state.shadowBlur}
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if mask != nil {
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if len(cv.shadowBuf) != 4 {
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panic("invalid number of points to fill with mask, must be 4")
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}
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var quad [4][2]float64
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copy(quad[:], cv.shadowBuf)
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cv.b.FillImageMask(&style, mask, quad)
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} else {
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cv.b.Fill(&style, cv.shadowBuf, canOverlap)
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}
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}
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