88 lines
2.2 KiB
Go
88 lines
2.2 KiB
Go
// Copyright 2010 The draw2d Authors. All rights reserved.
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// created: 21/11/2010 by Laurent Le Goff
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package draw2d
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import (
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"exp/draw"
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"image"
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"freetype-go.googlecode.com/hg/freetype/raster"
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)
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const M = 1<<16 - 1
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type NRGBAPainter struct {
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// The image to compose onto.
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Image *image.NRGBA
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// The Porter-Duff composition operator.
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Op draw.Op
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// The 16-bit color to paint the spans.
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cr, cg, cb, ca uint32
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}
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// Paint satisfies the Painter interface by painting ss onto an image.RGBA.
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func (r *NRGBAPainter) Paint(ss []raster.Span, done bool) {
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b := r.Image.Bounds()
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for _, s := range ss {
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if s.Y < b.Min.Y {
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continue
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}
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if s.Y >= b.Max.Y {
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return
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}
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if s.X0 < b.Min.X {
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s.X0 = b.Min.X
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}
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if s.X1 > b.Max.X {
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s.X1 = b.Max.X
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}
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if s.X0 >= s.X1 {
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continue
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}
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base := s.Y * r.Image.Stride
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p := r.Image.Pix[base+s.X0 : base+s.X1]
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// This code is duplicated from drawGlyphOver in $GOROOT/src/pkg/exp/draw/draw.go.
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// TODO(nigeltao): Factor out common code into a utility function, once the compiler
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// can inline such function calls.
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ma := s.A >> 16
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if r.Op == draw.Over {
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for i, nrgba := range p {
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dr, dg, db, da := nrgba.RGBA()
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a := M - (r.ca*ma)/M
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da = (da*a + r.ca*ma) / M
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if da != 0 {
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dr = minUint32(M, (dr*a+r.cr*ma)/da)
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dg = minUint32(M, (dg*a+r.cg*ma)/da)
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db = minUint32(M, (db*a+r.cb*ma)/da)
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} else {
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dr, dg, db = 0, 0, 0
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}
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p[i] = image.NRGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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} else {
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for i, nrgba := range p {
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dr, dg, db, da := nrgba.RGBA()
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a := M - ma
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da = (da*a + r.ca*ma) / M
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if da != 0 {
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dr = minUint32(M, (dr*a+r.cr*ma)/da)
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dg = minUint32(M, (dg*a+r.cg*ma)/da)
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db = minUint32(M, (db*a+r.cb*ma)/da)
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} else {
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dr, dg, db = 0, 0, 0
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}
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p[i] = image.NRGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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}
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}
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}
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// SetColor sets the color to paint the spans.
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func (r *NRGBAPainter) SetColor(c image.Color) {
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r.cr, r.cg, r.cb, r.ca = c.RGBA()
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}
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// NewRGBAPainter creates a new RGBAPainter for the given image.
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func NewNRGBAPainter(m *image.NRGBA) *NRGBAPainter {
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return &NRGBAPainter{Image: m}
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}
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