1 files changed, 206 insertions, 0 deletions

diff --git a/Godeps/_workspace/src/code.google.com/p/graphics-go/graphics/interp/bilinear.go b/Godeps/_workspace/src/code.google.com/p/graphics-go/graphics/interp/bilinear.go
new file mode 100644
index 000000000..e18321a15
--- /dev/null
+++ b/Godeps/_workspace/src/code.google.com/p/graphics-go/graphics/interp/bilinear.go
@@ -0,0 +1,206 @@
+// Copyright 2012 The Graphics-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package interp
+
+import (
+	"image"
+	"image/color"
+	"math"
+)
+
+// Bilinear implements bilinear interpolation.
+var Bilinear Interp = bilinear{}
+
+type bilinear struct{}
+
+func (i bilinear) Interp(src image.Image, x, y float64) color.Color {
+	if src, ok := src.(*image.RGBA); ok {
+		return i.RGBA(src, x, y)
+	}
+	return bilinearGeneral(src, x, y)
+}
+
+func bilinearGeneral(src image.Image, x, y float64) color.Color {
+	p := findLinearSrc(src.Bounds(), x, y)
+	var fr, fg, fb, fa float64
+	var r, g, b, a uint32
+
+	r, g, b, a = src.At(p.low.X, p.low.Y).RGBA()
+	fr += float64(r) * p.frac00
+	fg += float64(g) * p.frac00
+	fb += float64(b) * p.frac00
+	fa += float64(a) * p.frac00
+
+	r, g, b, a = src.At(p.high.X, p.low.Y).RGBA()
+	fr += float64(r) * p.frac01
+	fg += float64(g) * p.frac01
+	fb += float64(b) * p.frac01
+	fa += float64(a) * p.frac01
+
+	r, g, b, a = src.At(p.low.X, p.high.Y).RGBA()
+	fr += float64(r) * p.frac10
+	fg += float64(g) * p.frac10
+	fb += float64(b) * p.frac10
+	fa += float64(a) * p.frac10
+
+	r, g, b, a = src.At(p.high.X, p.high.Y).RGBA()
+	fr += float64(r) * p.frac11
+	fg += float64(g) * p.frac11
+	fb += float64(b) * p.frac11
+	fa += float64(a) * p.frac11
+
+	var c color.RGBA64
+	c.R = uint16(fr + 0.5)
+	c.G = uint16(fg + 0.5)
+	c.B = uint16(fb + 0.5)
+	c.A = uint16(fa + 0.5)
+	return c
+}
+
+func (bilinear) RGBA(src *image.RGBA, x, y float64) color.RGBA {
+	p := findLinearSrc(src.Bounds(), x, y)
+
+	// Array offsets for the surrounding pixels.
+	off00 := offRGBA(src, p.low.X, p.low.Y)
+	off01 := offRGBA(src, p.high.X, p.low.Y)
+	off10 := offRGBA(src, p.low.X, p.high.Y)
+	off11 := offRGBA(src, p.high.X, p.high.Y)
+
+	var fr, fg, fb, fa float64
+
+	fr += float64(src.Pix[off00+0]) * p.frac00
+	fg += float64(src.Pix[off00+1]) * p.frac00
+	fb += float64(src.Pix[off00+2]) * p.frac00
+	fa += float64(src.Pix[off00+3]) * p.frac00
+
+	fr += float64(src.Pix[off01+0]) * p.frac01
+	fg += float64(src.Pix[off01+1]) * p.frac01
+	fb += float64(src.Pix[off01+2]) * p.frac01
+	fa += float64(src.Pix[off01+3]) * p.frac01
+
+	fr += float64(src.Pix[off10+0]) * p.frac10
+	fg += float64(src.Pix[off10+1]) * p.frac10
+	fb += float64(src.Pix[off10+2]) * p.frac10
+	fa += float64(src.Pix[off10+3]) * p.frac10
+
+	fr += float64(src.Pix[off11+0]) * p.frac11
+	fg += float64(src.Pix[off11+1]) * p.frac11
+	fb += float64(src.Pix[off11+2]) * p.frac11
+	fa += float64(src.Pix[off11+3]) * p.frac11
+
+	var c color.RGBA
+	c.R = uint8(fr + 0.5)
+	c.G = uint8(fg + 0.5)
+	c.B = uint8(fb + 0.5)
+	c.A = uint8(fa + 0.5)
+	return c
+}
+
+func (bilinear) Gray(src *image.Gray, x, y float64) color.Gray {
+	p := findLinearSrc(src.Bounds(), x, y)
+
+	// Array offsets for the surrounding pixels.
+	off00 := offGray(src, p.low.X, p.low.Y)
+	off01 := offGray(src, p.high.X, p.low.Y)
+	off10 := offGray(src, p.low.X, p.high.Y)
+	off11 := offGray(src, p.high.X, p.high.Y)
+
+	var fc float64
+	fc += float64(src.Pix[off00]) * p.frac00
+	fc += float64(src.Pix[off01]) * p.frac01
+	fc += float64(src.Pix[off10]) * p.frac10
+	fc += float64(src.Pix[off11]) * p.frac11
+
+	var c color.Gray
+	c.Y = uint8(fc + 0.5)
+	return c
+}
+
+type bilinearSrc struct {
+	// Top-left and bottom-right interpolation sources
+	low, high image.Point
+	// Fraction of each pixel to take. The 0 suffix indicates
+	// top/left, and the 1 suffix indicates bottom/right.
+	frac00, frac01, frac10, frac11 float64
+}
+
+func findLinearSrc(b image.Rectangle, sx, sy float64) bilinearSrc {
+	maxX := float64(b.Max.X)
+	maxY := float64(b.Max.Y)
+	minX := float64(b.Min.X)
+	minY := float64(b.Min.Y)
+	lowX := math.Floor(sx - 0.5)
+	lowY := math.Floor(sy - 0.5)
+	if lowX < minX {
+		lowX = minX
+	}
+	if lowY < minY {
+		lowY = minY
+	}
+
+	highX := math.Ceil(sx - 0.5)
+	highY := math.Ceil(sy - 0.5)
+	if highX >= maxX {
+		highX = maxX - 1
+	}
+	if highY >= maxY {
+		highY = maxY - 1
+	}
+
+	// In the variables below, the 0 suffix indicates top/left, and the
+	// 1 suffix indicates bottom/right.
+
+	// Center of each surrounding pixel.
+	x00 := lowX + 0.5
+	y00 := lowY + 0.5
+	x01 := highX + 0.5
+	y01 := lowY + 0.5
+	x10 := lowX + 0.5
+	y10 := highY + 0.5
+	x11 := highX + 0.5
+	y11 := highY + 0.5
+
+	p := bilinearSrc{
+		low:  image.Pt(int(lowX), int(lowY)),
+		high: image.Pt(int(highX), int(highY)),
+	}
+
+	// Literally, edge cases. If we are close enough to the edge of
+	// the image, curtail the interpolation sources.
+	if lowX == highX && lowY == highY {
+		p.frac00 = 1.0
+	} else if sy-minY <= 0.5 && sx-minX <= 0.5 {
+		p.frac00 = 1.0
+	} else if maxY-sy <= 0.5 && maxX-sx <= 0.5 {
+		p.frac11 = 1.0
+	} else if sy-minY <= 0.5 || lowY == highY {
+		p.frac00 = x01 - sx
+		p.frac01 = sx - x00
+	} else if sx-minX <= 0.5 || lowX == highX {
+		p.frac00 = y10 - sy
+		p.frac10 = sy - y00
+	} else if maxY-sy <= 0.5 {
+		p.frac10 = x11 - sx
+		p.frac11 = sx - x10
+	} else if maxX-sx <= 0.5 {
+		p.frac01 = y11 - sy
+		p.frac11 = sy - y01
+	} else {
+		p.frac00 = (x01 - sx) * (y10 - sy)
+		p.frac01 = (sx - x00) * (y11 - sy)
+		p.frac10 = (x11 - sx) * (sy - y00)
+		p.frac11 = (sx - x10) * (sy - y01)
+	}
+
+	return p
+}
+
+// TODO(crawshaw): When we have inlining, consider func (p *RGBA) Off(x, y) int
+func offRGBA(src *image.RGBA, x, y int) int {
+	return (y-src.Rect.Min.Y)*src.Stride + (x-src.Rect.Min.X)*4
+}
+func offGray(src *image.Gray, x, y int) int {
+	return (y-src.Rect.Min.Y)*src.Stride + (x - src.Rect.Min.X)
+}