// Copyright 2015 The 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.
//go:generate go run gen.go
package draw
import (
"image"
"image/color"
"math"
"sync"
"golang.org/x/image/math/f64"
)
// Copy copies the part of the source image defined by src and sr and writes
// the result of a Porter-Duff composition to the part of the destination image
// defined by dst and the translation of sr so that sr.Min translates to dp.
func Copy(dst Image, dp image.Point, src image.Image, sr image.Rectangle, op Op, opts *Options) {
var o Options
if opts != nil {
o = *opts
}
dr := sr.Add(dp.Sub(sr.Min))
if o.DstMask == nil {
DrawMask(dst, dr, src, sr.Min, o.SrcMask, o.SrcMaskP.Add(sr.Min), op)
} else {
NearestNeighbor.Scale(dst, dr, src, sr, op, opts)
}
}
// Scaler scales the part of the source image defined by src and sr and writes
// the result of a Porter-Duff composition to the part of the destination image
// defined by dst and dr.
//
// A Scaler is safe to use concurrently.
type Scaler interface {
Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options)
}
// Transformer transforms the part of the source image defined by src and sr
// and writes the result of a Porter-Duff composition to the part of the
// destination image defined by dst and the affine transform m applied to sr.
//
// For example, if m is the matrix
//
// m00 m01 m02
// m10 m11 m12
//
// then the src-space point (sx, sy) maps to the dst-space point
// (m00*sx + m01*sy + m02, m10*sx + m11*sy + m12).
//
// A Transformer is safe to use concurrently.
type Transformer interface {
Transform(dst Image, m f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options)
}
// Options are optional parameters to Copy, Scale and Transform.
//
// A nil *Options means to use the default (zero) values of each field.
type Options struct {
// Masks limit what parts of the dst image are drawn to and what parts of
// the src image are drawn from.
//
// A dst or src mask image having a zero alpha (transparent) pixel value in
// the respective coordinate space means that dst pixel is entirely
// unaffected or that src pixel is considered transparent black. A full
// alpha (opaque) value means that the dst pixel is maximally affected or
// the src pixel contributes maximally. The default values, nil, are
// equivalent to fully opaque, infinitely large mask images.
//
// The DstMask is otherwise known as a clip mask, and its pixels map 1:1 to
// the dst image's pixels. DstMaskP in DstMask space corresponds to
// image.Point{X:0, Y:0} in dst space. For example, when limiting
// repainting to a 'dirty rectangle', use that image.Rectangle and a zero
// image.Point as the DstMask and DstMaskP.
//
// The SrcMask's pixels map 1:1 to the src image's pixels. SrcMaskP in
// SrcMask space corresponds to image.Point{X:0, Y:0} in src space. For
// example, when drawing font glyphs in a uniform color, use an
// *image.Uniform as the src, and use the glyph atlas image and the
// per-glyph offset as SrcMask and SrcMaskP:
// Copy(dst, dp, image.NewUniform(color), image.Rect(0, 0, glyphWidth, glyphHeight), &Options{
// SrcMask: glyphAtlas,
// SrcMaskP: glyphOffset,
// })
DstMask image.Image
DstMaskP image.Point
SrcMask image.Image
SrcMaskP image.Point
// TODO: a smooth vs sharp edges option, for arbitrary rotations?
}
// Interpolator is an interpolation algorithm, when dst and src pixels don't
// have a 1:1 correspondence.
//
// Of the interpolators provided by this package:
// - NearestNeighbor is fast but usually looks worst.
// - CatmullRom is slow but usually looks best.
// - ApproxBiLinear has reasonable speed and quality.
//
// The time taken depends on the size of dr. For kernel interpolators, the
// speed also depends on the size of sr, and so are often slower than
// non-kernel interpolators, especially when scaling down.
type Interpolator interface {
Scaler
Transformer
}
// Kernel is an interpolator that blends source pixels weighted by a symmetric
// kernel function.
type Kernel struct {
// Support is the kernel support and must be >= 0. At(t) is assumed to be
// zero when t >= Support.
Support float64
// At is the kernel function. It will only be called with t in the
// range [0, Support).
At func(t float64) float64
}
// Scale implements the Scaler interface.
func (q *Kernel) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, op Op, opts *Options) {
q.newScaler(dr.Dx(), dr.Dy(), sr.Dx(), sr.Dy(), false).Scale(dst, dr, src, sr, op, opts)
}
// NewScaler returns a Scaler that is optimized for scaling multiple times with
// the same fixed destination and source width and height.
func (q *Kernel) NewScaler(dw, dh, sw, sh int) Scaler {
return q.newScaler(dw, dh, sw, sh, true)
}
func (q *Kernel) newScaler(dw, dh, sw, sh int, usePool bool) Scaler {
z := &kernelScaler{
kernel: q,
dw: int32(dw),
dh: int32(dh),
sw: int32(sw),
sh: int32(sh),
horizontal: newDistrib(q, int32(dw), int32(sw)),
vertical: newDistrib(q, int32(dh), int32(sh)),
}
if usePool {
z.pool.New = func() interface{} {
tmp := z.makeTmpBuf()
return &tmp
}
}
return z
}
var (
// NearestNeighbor is the nearest neighbor interpolator. It is very fast,
// but usually gives very low quality results. When scaling up, the result
// will look 'blocky'.
NearestNeighbor = Interpolator(nnInterpolator{})
// ApproxBiLinear is a mixture of the nearest neighbor and bi-linear
// interpolators. It is fast, but usually gives medium quality results.
//
// It implements bi-linear interpolation when upscaling and a bi-linear
// blend of the 4 nearest neighbor pixels when downscaling. This yields
// nicer quality than nearest neighbor interpolation when upscaling, but
// the time taken is independent of the number of source pixels, unlike the
// bi-linear interpolator. When downscaling a large image, the performance
// difference can be significant.
ApproxBiLinear = Interpolator(ablInterpolator{})
// BiLinear is the tent kernel. It is slow, but usually gives high quality
// results.
BiLinear = &Kernel{1, func(t float64) float64 {
return 1 - t
}}
// CatmullRom is the Catmull-Rom kernel. It is very slow, but usually gives
// very high quality results.
//
// It is an instance of the more general cubic BC-spline kernel with parameters
// B=0 and C=0.5. See Mitchell and Netravali, "Reconstruction Filters in
// Computer Graphics", Computer Graphics, Vol. 22, No. 4, pp. 221-228.
CatmullRom = &Kernel{2, func(t float64) float64 {
if t < 1 {
return (1.5*t-2.5)*t*t + 1
}
return ((-0.5*t+2.5)*t-4)*t + 2
}}
// TODO: a Kaiser-Bessel kernel?
)
type nnInterpolator struct{}
type ablInterpolator struct{}
type kernelScaler struct {
kernel *Kernel
dw, dh, sw, sh int32
horizontal, vertical distrib
pool sync.Pool
}
func (z *kernelScaler) makeTmpBuf() [][4]float64 {
return make([][4]float64, z.dw*z.sh)
}
// source is a range of contribs, their inverse total weight, and that ITW
// divided by 0xffff.
type source struct {
i, j int32
invTotalWeight float64
invTotalWeightFFFF float64
}
// contrib is the weight of a column or row.
type contrib struct {
coord int32
weight float64
}
// distrib measures how source pixels are distributed over destination pixels.
type distrib struct {
// sources are what contribs each column or row in the source image owns,
// and the total weight of those contribs.
sources []source
// contribs are the contributions indexed by sources[s].i and sources[s].j.
contribs []contrib
}
// newDistrib returns a distrib that distributes sw source columns (or rows)
// over dw destination columns (or rows).
func newDistrib(q *Kernel, dw, sw int32) distrib {
scale := float64(sw) / float64(dw)
halfWidth, kernelArgScale := q.Support, 1.0
// When shrinking, broaden the effective kernel support so that we still
// visit every source pixel.
if scale > 1 {
halfWidth *= scale
kernelArgScale = 1 / scale
}
// Make the sources slice, one source for each column or row, and temporarily
// appropriate its elements' fields so that invTotalWeight is the scaled
// coordinate of the source column or row, and i and j are the lower and
// upper bounds of the range of destination columns or rows affected by the
// source column or row.
n, sources := int32(0), make([]source, dw)
for x := range sources {
center := (float64(x)+0.5)*scale - 0.5
i := int32(math.Floor(center - halfWidth))
if i < 0 {
i = 0
}
j := int32(math.Ceil(center + halfWidth))
if j > sw {
j = sw
if j < i {
j = i
}
}
sources[x] = source{i: i, j: j, invTotalWeight: center}
n += j - i
}
contribs := make([]contrib, 0, n)
for k, b := range sources {
totalWeight := 0.0
l := int32(len(contribs))
for coord := b.i; coord < b.j; coord++ {
t := abs((b.invTotalWeight - float64(coord)) * kernelArgScale)
if t >= q.Support {
continue
}
weight := q.At(t)
if weight == 0 {
continue
}
totalWeight += weight
contribs = append(contribs, contrib{coord, weight})
}
totalWeight = 1 / totalWeight
sources[k] = source{
i: l,
j: int32(len(contribs)),
invTotalWeight: totalWeight,
invTotalWeightFFFF: totalWeight / 0xffff,
}
}
return distrib{sources, contribs}
}
// abs is like math.Abs, but it doesn't care about negative zero, infinities or
// NaNs.
func abs(f float64) float64 {
if f < 0 {
f = -f
}
return f
}
// ftou converts the range [0.0, 1.0] to [0, 0xffff].
func ftou(f float64) uint16 {
i := int32(0xffff*f + 0.5)
if i > 0xffff {
return 0xffff
}
if i > 0 {
return uint16(i)
}
return 0
}
// fffftou converts the range [0.0, 65535.0] to [0, 0xffff].
func fffftou(f float64) uint16 {
i := int32(f + 0.5)
if i > 0xffff {
return 0xffff
}
if i > 0 {
return uint16(i)
}
return 0
}
// invert returns the inverse of m.
//
// TODO: move this into the f64 package, once we work out the convention for
// matrix methods in that package: do they modify the receiver, take a dst
// pointer argument, or return a new value?
func invert(m *f64.Aff3) f64.Aff3 {
m00 := +m[3*1+1]
m01 := -m[3*0+1]
m02 := +m[3*1+2]*m[3*0+1] - m[3*1+1]*m[3*0+2]
m10 := -m[3*1+0]
m11 := +m[3*0+0]
m12 := +m[3*1+0]*m[3*0+2] - m[3*1+2]*m[3*0+0]
det := m00*m11 - m10*m01
return f64.Aff3{
m00 / det,
m01 / det,
m02 / det,
m10 / det,
m11 / det,
m12 / det,
}
}
func matMul(p, q *f64.Aff3) f64.Aff3 {
return f64.Aff3{
p[3*0+0]*q[3*0+0] + p[3*0+1]*q[3*1+0],
p[3*0+0]*q[3*0+1] + p[3*0+1]*q[3*1+1],
p[3*0+0]*q[3*0+2] + p[3*0+1]*q[3*1+2] + p[3*0+2],
p[3*1+0]*q[3*0+0] + p[3*1+1]*q[3*1+0],
p[3*1+0]*q[3*0+1] + p[3*1+1]*q[3*1+1],
p[3*1+0]*q[3*0+2] + p[3*1+1]*q[3*1+2] + p[3*1+2],
}
}
// transformRect returns a rectangle dr that contains sr transformed by s2d.
func transformRect(s2d *f64.Aff3, sr *image.Rectangle) (dr image.Rectangle) {
ps := [...]image.Point{
{sr.Min.X, sr.Min.Y},
{sr.Max.X, sr.Min.Y},
{sr.Min.X, sr.Max.Y},
{sr.Max.X, sr.Max.Y},
}
for i, p := range ps {
sxf := float64(p.X)
syf := float64(p.Y)
dx := int(math.Floor(s2d[0]*sxf + s2d[1]*syf + s2d[2]))
dy := int(math.Floor(s2d[3]*sxf + s2d[4]*syf + s2d[5]))
// The +1 adjustments below are because an image.Rectangle is inclusive
// on the low end but exclusive on the high end.
if i == 0 {
dr = image.Rectangle{
Min: image.Point{dx + 0, dy + 0},
Max: image.Point{dx + 1, dy + 1},
}
continue
}
if dr.Min.X > dx {
dr.Min.X = dx
}
dx++
if dr.Max.X < dx {
dr.Max.X = dx
}
if dr.Min.Y > dy {
dr.Min.Y = dy
}
dy++
if dr.Max.Y < dy {
dr.Max.Y = dy
}
}
return dr
}
func clipAffectedDestRect(adr image.Rectangle, dstMask image.Image, dstMaskP image.Point) (image.Rectangle, image.Image) {
if dstMask == nil {
return adr, nil
}
if r, ok := dstMask.(image.Rectangle); ok {
return adr.Intersect(r.Sub(dstMaskP)), nil
}
// TODO: clip to dstMask.Bounds() if the color model implies that out-of-bounds means 0 alpha?
return adr, dstMask
}
func transform_Uniform(dst Image, dr, adr image.Rectangle, d2s *f64.Aff3, src *image.Uniform, sr image.Rectangle, bias image.Point, op Op) {
switch op {
case Over:
switch dst := dst.(type) {
case *image.RGBA:
pr, pg, pb, pa := src.C.RGBA()
pa1 := (0xffff - pa) * 0x101
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
d := dst.PixOffset(dr.Min.X+adr.Min.X, dr.Min.Y+int(dy))
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx, d = dx+1, d+4 {
dxf := float64(dr.Min.X+int(dx)) + 0.5
sx0 := int(d2s[0]*dxf+d2s[1]*dyf+d2s[2]) + bias.X
sy0 := int(d2s[3]*dxf+d2s[4]*dyf+d2s[5]) + bias.Y
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
dst.Pix[d+0] = uint8((uint32(dst.Pix[d+0])*pa1/0xffff + pr) >> 8)
dst.Pix[d+1] = uint8((uint32(dst.Pix[d+1])*pa1/0xffff + pg) >> 8)
dst.Pix[d+2] = uint8((uint32(dst.Pix[d+2])*pa1/0xffff + pb) >> 8)
dst.Pix[d+3] = uint8((uint32(dst.Pix[d+3])*pa1/0xffff + pa) >> 8)
}
}
default:
pr, pg, pb, pa := src.C.RGBA()
pa1 := 0xffff - pa
dstColorRGBA64 := &color.RGBA64{}
dstColor := color.Color(dstColorRGBA64)
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ {
dxf := float64(dr.Min.X+int(dx)) + 0.5
sx0 := int(d2s[0]*dxf+d2s[1]*dyf+d2s[2]) + bias.X
sy0 := int(d2s[3]*dxf+d2s[4]*dyf+d2s[5]) + bias.Y
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
qr, qg, qb, qa := dst.At(dr.Min.X+int(dx), dr.Min.Y+int(dy)).RGBA()
dstColorRGBA64.R = uint16(qr*pa1/0xffff + pr)
dstColorRGBA64.G = uint16(qg*pa1/0xffff + pg)
dstColorRGBA64.B = uint16(qb*pa1/0xffff + pb)
dstColorRGBA64.A = uint16(qa*pa1/0xffff + pa)
dst.Set(dr.Min.X+int(dx), dr.Min.Y+int(dy), dstColor)
}
}
}
case Src:
switch dst := dst.(type) {
case *image.RGBA:
pr, pg, pb, pa := src.C.RGBA()
pr8 := uint8(pr >> 8)
pg8 := uint8(pg >> 8)
pb8 := uint8(pb >> 8)
pa8 := uint8(pa >> 8)
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
d := dst.PixOffset(dr.Min.X+adr.Min.X, dr.Min.Y+int(dy))
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx, d = dx+1, d+4 {
dxf := float64(dr.Min.X+int(dx)) + 0.5
sx0 := int(d2s[0]*dxf+d2s[1]*dyf+d2s[2]) + bias.X
sy0 := int(d2s[3]*dxf+d2s[4]*dyf+d2s[5]) + bias.Y
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
dst.Pix[d+0] = pr8
dst.Pix[d+1] = pg8
dst.Pix[d+2] = pb8
dst.Pix[d+3] = pa8
}
}
default:
pr, pg, pb, pa := src.C.RGBA()
dstColorRGBA64 := &color.RGBA64{
uint16(pr),
uint16(pg),
uint16(pb),
uint16(pa),
}
dstColor := color.Color(dstColorRGBA64)
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ {
dxf := float64(dr.Min.X+int(dx)) + 0.5
sx0 := int(d2s[0]*dxf+d2s[1]*dyf+d2s[2]) + bias.X
sy0 := int(d2s[3]*dxf+d2s[4]*dyf+d2s[5]) + bias.Y
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
dst.Set(dr.Min.X+int(dx), dr.Min.Y+int(dy), dstColor)
}
}
}
}
}
func opaque(m image.Image) bool {
o, ok := m.(interface {
Opaque() bool
})
return ok && o.Opaque()
}
