151 lines
5 KiB
Go
151 lines
5 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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// see http://pippin.gimp.org/image_processing/chap_resampling.html
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package draw2dimg
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import (
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"github.com/llgcode/draw2d"
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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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type ImageFilter int
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const (
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LinearFilter ImageFilter = iota
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BilinearFilter
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BicubicFilter
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M = 1<<16 - 1
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)
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//see http://pippin.gimp.org/image_processing/chap_resampling.html
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func getColorLinear(img image.Image, x, y float64) color.Color {
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return img.At(int(x), int(y))
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}
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func getColorBilinear(img image.Image, x, y float64) color.Color {
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x0 := math.Floor(x)
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y0 := math.Floor(y)
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dx := x - x0
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dy := y - y0
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rt, gt, bt, at := img.At(int(x0), int(y0)).RGBA()
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r0, g0, b0, a0 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = img.At(int(x0+1), int(y0)).RGBA()
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r1, g1, b1, a1 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = img.At(int(x0+1), int(y0+1)).RGBA()
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r2, g2, b2, a2 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = img.At(int(x0), int(y0+1)).RGBA()
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r3, g3, b3, a3 := float64(rt), float64(gt), float64(bt), float64(at)
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r := int(lerp(lerp(r0, r1, dx), lerp(r3, r2, dx), dy))
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g := int(lerp(lerp(g0, g1, dx), lerp(g3, g2, dx), dy))
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b := int(lerp(lerp(b0, b1, dx), lerp(b3, b2, dx), dy))
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a := int(lerp(lerp(a0, a1, dx), lerp(a3, a2, dx), dy))
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return color.RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
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}
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/**
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-- LERP
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-- /lerp/, vi.,n.
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--
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-- Quasi-acronym for Linear Interpolation, used as a verb or noun for
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-- the operation. "Bresenham's algorithm lerps incrementally between the
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-- two endpoints of the line." (From Jargon File (4.4.4, 14 Aug 2003)
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*/
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func lerp(v1, v2, ratio float64) float64 {
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return v1*(1-ratio) + v2*ratio
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}
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func getColorCubicRow(img image.Image, x, y, offset float64) color.Color {
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c0 := img.At(int(x), int(y))
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c1 := img.At(int(x+1), int(y))
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c2 := img.At(int(x+2), int(y))
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c3 := img.At(int(x+3), int(y))
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rt, gt, bt, at := c0.RGBA()
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r0, g0, b0, a0 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c1.RGBA()
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r1, g1, b1, a1 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c2.RGBA()
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r2, g2, b2, a2 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c3.RGBA()
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r3, g3, b3, a3 := float64(rt), float64(gt), float64(bt), float64(at)
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r, g, b, a := cubic(offset, r0, r1, r2, r3), cubic(offset, g0, g1, g2, g3), cubic(offset, b0, b1, b2, b3), cubic(offset, a0, a1, a2, a3)
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return color.RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
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}
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func getColorBicubic(img image.Image, x, y float64) color.Color {
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x0 := math.Floor(x)
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y0 := math.Floor(y)
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dx := x - x0
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dy := y - y0
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c0 := getColorCubicRow(img, x0-1, y0-1, dx)
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c1 := getColorCubicRow(img, x0-1, y0, dx)
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c2 := getColorCubicRow(img, x0-1, y0+1, dx)
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c3 := getColorCubicRow(img, x0-1, y0+2, dx)
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rt, gt, bt, at := c0.RGBA()
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r0, g0, b0, a0 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c1.RGBA()
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r1, g1, b1, a1 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c2.RGBA()
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r2, g2, b2, a2 := float64(rt), float64(gt), float64(bt), float64(at)
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rt, gt, bt, at = c3.RGBA()
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r3, g3, b3, a3 := float64(rt), float64(gt), float64(bt), float64(at)
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r, g, b, a := cubic(dy, r0, r1, r2, r3), cubic(dy, g0, g1, g2, g3), cubic(dy, b0, b1, b2, b3), cubic(dy, a0, a1, a2, a3)
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return color.RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
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}
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func cubic(offset, v0, v1, v2, v3 float64) uint32 {
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// offset is the offset of the sampled value between v1 and v2
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return uint32(((((-7*v0+21*v1-21*v2+7*v3)*offset+
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(15*v0-36*v1+27*v2-6*v3))*offset+
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(-9*v0+9*v2))*offset + (v0 + 16*v1 + v2)) / 18.0)
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}
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func DrawImage(src image.Image, dest draw.Image, tr draw2d.MatrixTransform, op draw.Op, filter ImageFilter) {
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bounds := src.Bounds()
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x0, y0, x1, y1 := tr.TransformRectangle(float64(bounds.Min.X), float64(bounds.Min.Y), float64(bounds.Max.X), float64(bounds.Max.Y))
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var x, y, u, v float64
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var c1, c2, cr color.Color
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var r, g, b, a, ia, r1, g1, b1, a1, r2, g2, b2, a2 uint32
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var color color.RGBA
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for x = x0; x < x1; x++ {
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for y = y0; y < y1; y++ {
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u = x
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v = y
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u, v = tr.InverseTransformPoint(u, v)
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if bounds.Min.X <= int(u) && bounds.Max.X > int(u) && bounds.Min.Y <= int(v) && bounds.Max.Y > int(v) {
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c1 = dest.At(int(x), int(y))
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switch filter {
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case LinearFilter:
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c2 = src.At(int(u), int(v))
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case BilinearFilter:
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c2 = getColorBilinear(src, u, v)
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case BicubicFilter:
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c2 = getColorBicubic(src, u, v)
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}
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switch op {
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case draw.Over:
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r1, g1, b1, a1 = c1.RGBA()
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r2, g2, b2, a2 = c2.RGBA()
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ia = M - a2
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r = ((r1 * ia) / M) + r2
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g = ((g1 * ia) / M) + g2
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b = ((b1 * ia) / M) + b2
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a = ((a1 * ia) / M) + a2
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color.R = uint8(r >> 8)
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color.G = uint8(g >> 8)
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color.B = uint8(b >> 8)
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color.A = uint8(a >> 8)
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cr = color
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default:
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cr = c2
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}
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dest.Set(int(x), int(y), cr)
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}
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}
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}
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}
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