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Image rotation refactoring
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@disintegration
disintegration committed Sep 25, 2016
1 parent c369f58 commit d3ddfc5
Showing 1 changed file with 120 additions and 112 deletions.
232 changes: 120 additions & 112 deletions transform.go
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Original file line number Diff line number Diff line change
Expand Up @@ -214,131 +214,139 @@ func (p *rotateFilter) Draw(dst draw.Image, src image.Image, options *Options) {

xf, yf := rotatePoint(float32(x)-dstxoff, float32(y)-dstyoff, asin, acos)
xf, yf = float32(srcb.Min.X)+xf+srcxoff, float32(srcb.Min.Y)+yf+srcyoff
var px pixel

switch p.interpolation {
case CubicInterpolation:
var calc bool
var pxs [16]pixel
var cfs [16]float32
var px pixel

x0, y0 := int(floorf32(xf)), int(floorf32(yf))
xq, yq := xf-float32(x0), yf-float32(y0)

for i := 0; i < 4; i++ {
for j := 0; j < 4; j++ {
pt := image.Pt(x0+j-1, y0+i-1)
if pt.In(srcb) {
pxs[i*4+j] = pixGetter.getPixel(pt.X, pt.Y)
calc = true
} else {
pxs[i*4+j] = bgpx
}
}
}

if !calc {
pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, bgpx)
continue
}

cfs[0] = (1.0 / 36.0) * xq * yq * (xq - 1) * (xq - 2) * (yq - 1) * (yq - 2)
cfs[1] = -(1.0 / 12.0) * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq - 2)
cfs[2] = (1.0 / 12.0) * xq * yq * (xq + 1) * (xq - 2) * (yq - 1) * (yq - 2)
cfs[3] = -(1.0 / 36.0) * xq * yq * (xq - 1) * (xq + 1) * (yq - 1) * (yq - 2)
cfs[4] = -(1.0 / 12.0) * xq * (xq - 1) * (xq - 2) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[5] = 0.25 * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[6] = -0.25 * xq * (xq + 1) * (xq - 2) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[7] = (1.0 / 12.0) * xq * (xq - 1) * (xq + 1) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[8] = (1.0 / 12.0) * xq * yq * (xq - 1) * (xq - 2) * (yq + 1) * (yq - 2)
cfs[9] = -0.25 * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq + 1) * (yq - 2)
cfs[10] = 0.25 * xq * yq * (xq + 1) * (xq - 2) * (yq + 1) * (yq - 2)
cfs[11] = -(1.0 / 12.0) * xq * yq * (xq - 1) * (xq + 1) * (yq + 1) * (yq - 2)
cfs[12] = -(1.0 / 36.0) * xq * yq * (xq - 1) * (xq - 2) * (yq - 1) * (yq + 1)
cfs[13] = (1.0 / 12.0) * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq + 1)
cfs[14] = -(1.0 / 12.0) * xq * yq * (xq + 1) * (xq - 2) * (yq - 1) * (yq + 1)
cfs[15] = (1.0 / 36.0) * xq * yq * (xq - 1) * (xq + 1) * (yq - 1) * (yq + 1)

for i := range pxs {
wa := pxs[i].A * cfs[i]
px.R += pxs[i].R * wa
px.G += pxs[i].G * wa
px.B += pxs[i].B * wa
px.A += wa
}

if px.A != 0.0 {
px.R /= px.A
px.G /= px.A
px.B /= px.A
}

pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, px)

px = interpolateCubic(xf, yf, srcb, pixGetter, bgpx)
case LinearInterpolation:
var calc bool
var pxs [4]pixel
var cfs [4]float32
var px pixel

x0, y0 := int(floorf32(xf)), int(floorf32(yf))
xq, yq := xf-float32(x0), yf-float32(y0)

for i := 0; i < 2; i++ {
for j := 0; j < 2; j++ {
pt := image.Pt(x0+j, y0+i)
if pt.In(srcb) {
pxs[i*2+j] = pixGetter.getPixel(pt.X, pt.Y)
calc = true
} else {
pxs[i*2+j] = bgpx
}
}
}

if !calc {
pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, bgpx)
continue
}

cfs[0] = (1 - xq) * (1 - yq)
cfs[1] = xq * (1 - yq)
cfs[2] = (1 - xq) * yq
cfs[3] = xq * yq

for i := range pxs {
wa := pxs[i].A * cfs[i]
px.R += pxs[i].R * wa
px.G += pxs[i].G * wa
px.B += pxs[i].B * wa
px.A += wa
}

if px.A != 0.0 {
px.R /= px.A
px.G /= px.A
px.B /= px.A
}

pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, px)

px = interpolateLinear(xf, yf, srcb, pixGetter, bgpx)
default:
var px pixel
x0, y0 := int(floorf32(xf+0.5)), int(floorf32(yf+0.5))
if image.Pt(x0, y0).In(srcb) {
px = pixGetter.getPixel(x0, y0)
} else {
px = bgpx
}
pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, px)
px = interpolateNearest(xf, yf, srcb, pixGetter, bgpx)
}

pixSetter.setPixel(dstb.Min.X+x, dstb.Min.Y+y, px)
}
}
})

return
}

func interpolateCubic(xf, yf float32, bounds image.Rectangle, pixGetter *pixelGetter, bgpx pixel) pixel {
var pxs [16]pixel
var cfs [16]float32
var px pixel

x0, y0 := int(floorf32(xf)), int(floorf32(yf))
if !image.Pt(x0, y0).In(image.Rect(bounds.Min.X-1, bounds.Min.Y-1, bounds.Max.X, bounds.Max.Y)) {
return bgpx
}
xq, yq := xf-float32(x0), yf-float32(y0)

for i := 0; i < 4; i++ {
for j := 0; j < 4; j++ {
pt := image.Pt(x0+j-1, y0+i-1)
if pt.In(bounds) {
pxs[i*4+j] = pixGetter.getPixel(pt.X, pt.Y)
} else {
pxs[i*4+j] = bgpx
}
}
}

const (
k04 = 1.0 / 4.0
k12 = 1.0 / 12.0
k36 = 1.0 / 36.0
)

cfs[0] = k36 * xq * yq * (xq - 1) * (xq - 2) * (yq - 1) * (yq - 2)
cfs[1] = -k12 * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq - 2)
cfs[2] = k12 * xq * yq * (xq + 1) * (xq - 2) * (yq - 1) * (yq - 2)
cfs[3] = -k36 * xq * yq * (xq - 1) * (xq + 1) * (yq - 1) * (yq - 2)
cfs[4] = -k12 * xq * (xq - 1) * (xq - 2) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[5] = k04 * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[6] = -k04 * xq * (xq + 1) * (xq - 2) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[7] = k12 * xq * (xq - 1) * (xq + 1) * (yq - 1) * (yq - 2) * (yq + 1)
cfs[8] = k12 * xq * yq * (xq - 1) * (xq - 2) * (yq + 1) * (yq - 2)
cfs[9] = -k04 * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq + 1) * (yq - 2)
cfs[10] = k04 * xq * yq * (xq + 1) * (xq - 2) * (yq + 1) * (yq - 2)
cfs[11] = -k12 * xq * yq * (xq - 1) * (xq + 1) * (yq + 1) * (yq - 2)
cfs[12] = -k36 * xq * yq * (xq - 1) * (xq - 2) * (yq - 1) * (yq + 1)
cfs[13] = k12 * yq * (xq - 1) * (xq - 2) * (xq + 1) * (yq - 1) * (yq + 1)
cfs[14] = -k12 * xq * yq * (xq + 1) * (xq - 2) * (yq - 1) * (yq + 1)
cfs[15] = k36 * xq * yq * (xq - 1) * (xq + 1) * (yq - 1) * (yq + 1)

for i := range pxs {
wa := pxs[i].A * cfs[i]
px.R += pxs[i].R * wa
px.G += pxs[i].G * wa
px.B += pxs[i].B * wa
px.A += wa
}

if px.A != 0.0 {
px.R /= px.A
px.G /= px.A
px.B /= px.A
}

return px
}

func interpolateLinear(xf, yf float32, bounds image.Rectangle, pixGetter *pixelGetter, bgpx pixel) pixel {
var pxs [4]pixel
var cfs [4]float32
var px pixel

x0, y0 := int(floorf32(xf)), int(floorf32(yf))
if !image.Pt(x0, y0).In(image.Rect(bounds.Min.X-1, bounds.Min.Y-1, bounds.Max.X, bounds.Max.Y)) {
return bgpx
}
xq, yq := xf-float32(x0), yf-float32(y0)

for i := 0; i < 2; i++ {
for j := 0; j < 2; j++ {
pt := image.Pt(x0+j, y0+i)
if pt.In(bounds) {
pxs[i*2+j] = pixGetter.getPixel(pt.X, pt.Y)
} else {
pxs[i*2+j] = bgpx
}
}
}

cfs[0] = (1 - xq) * (1 - yq)
cfs[1] = xq * (1 - yq)
cfs[2] = (1 - xq) * yq
cfs[3] = xq * yq

for i := range pxs {
wa := pxs[i].A * cfs[i]
px.R += pxs[i].R * wa
px.G += pxs[i].G * wa
px.B += pxs[i].B * wa
px.A += wa
}

if px.A != 0.0 {
px.R /= px.A
px.G /= px.A
px.B /= px.A
}

return px
}

func interpolateNearest(xf, yf float32, bounds image.Rectangle, pixGetter *pixelGetter, bgpx pixel) pixel {
x0, y0 := int(floorf32(xf+0.5)), int(floorf32(yf+0.5))
if image.Pt(x0, y0).In(bounds) {
return pixGetter.getPixel(x0, y0)
}
return bgpx
}

// Rotate creates a filter that rotates an image by the given angle counter-clockwise.
// The angle parameter is the rotation angle in degrees.
// The backgroundColor parameter specifies the color of the uncovered zone after the rotation.
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