// Change the aspect ratio of a rectangle.
// The mode can be "area", "width", "height", "fit", "fill" or "stretch".
// Panics if mode is empty or unrecognized.
func SetAspect(w, h, aspect float64, mode string) (float64, float64) {
switch mode {
case "area":
// aspect = width / height
// width = height * aspect
// width^2 = width * height * aspect
// height = width / aspect
// height^2 = width * height / aspect
w, h = math.Sqrt(w*h*aspect), math.Sqrt(w*h/aspect)
case "width":
// Set height from width.
h = w / aspect
case "height":
// Set width from height.
w = h * aspect
case "fit":
// Shrink one dimension.
w, h = math.Min(w, h*aspect), math.Min(h, w/aspect)
case "fill":
// Grow one dimension.
w, h = math.Max(w, h*aspect), math.Max(h, w/aspect)
case "stretch":
// Do nothing.
case "":
panic("no mode specified")
default:
panic("unknown mode: " + mode)
}
return w, h
}
// AdjustSigmoid changes the contrast of the image using a sigmoidal function and returns the adjusted image.
// It's a non-linear contrast change useful for photo adjustments as it preserves highlight and shadow detail.
// The midpoint parameter is the midpoint of contrast that must be between 0 and 1, typically 0.5.
// The factor parameter indicates how much to increase or decrease the contrast, typically in range (-10, 10).
// If the factor parameter is positive the image contrast is increased otherwise the contrast is decreased.
//
// Examples:
//
// dstImage = imaging.AdjustSigmoid(srcImage, 0.5, 3.0) // increase the contrast
// dstImage = imaging.AdjustSigmoid(srcImage, 0.5, -3.0) // decrease the contrast
//
func AdjustSigmoid(img image.Image, midpoint, factor float64) *image.NRGBA {
if factor == 0 {
return Clone(img)
}
lut := make([]uint8, 256)
a := math.Min(math.Max(midpoint, 0.0), 1.0)
b := math.Abs(factor)
sig0 := sigmoid(a, b, 0)
sig1 := sigmoid(a, b, 1)
e := 1.0e-6
if factor > 0 {
for i := 0; i < 256; i++ {
x := float64(i) / 255.0
sigX := sigmoid(a, b, x)
f := (sigX - sig0) / (sig1 - sig0)
lut[i] = clamp(f * 255.0)
}
} else {
for i := 0; i < 256; i++ {
x := float64(i) / 255.0
arg := math.Min(math.Max((sig1-sig0)*x+sig0, e), 1.0-e)
f := a - math.Log(1.0/arg-1.0)/b
lut[i] = clamp(f * 255.0)
}
}
fn := func(c color.NRGBA) color.NRGBA {
return color.NRGBA{lut[c.R], lut[c.G], lut[c.B], c.A}
}
return AdjustFunc(img, fn)
}
func (b *Bounds) ExtendPointZ(pointZ PointZ) *Bounds {
b.Min.X = math.Min(b.Min.X, pointZ.X)
b.Min.Y = math.Min(b.Min.Y, pointZ.Y)
b.Max.X = math.Max(b.Max.X, pointZ.X)
b.Max.Y = math.Max(b.Max.Y, pointZ.Y)
return b
}
func distanceRectRect(rect1 Rect, rect2 Rect) float64 {
var d float64 = 10000
for _, point := range rect1.MakeCorners() {
d = math.Min(d, distancePointRect(point, rect2))
if d < 1 {
return d
}
}
for _, point := range rect2.MakeCorners() {
d = math.Min(d, distancePointRect(point, rect1))
if d < 1 {
return d
}
}
for _, line := range rect1.MakeLines() {
d = math.Min(d, distanceLineRect(line, rect2))
if d < 1 {
return d
}
}
return d
}
func (v3 *Vector3) Min(v *Vector3) *Vector3 {
v3.X = math.Min(v3.X, v.X)
v3.Y = math.Min(v3.Y, v.Y)
v3.Z = math.Min(v3.Z, v.Z)
return v3
}
func subtractPSF(psf []float32,
psfWidth uint64,
residual []float32,
residualWidth uint64,
peakPos uint64, psfPeakPos uint64,
absPeakVal float32,
gain float32) {
var rx = float64(xpos(peakPos, residualWidth))
var ry = float64(ypos(peakPos, residualWidth))
var px = float64(xpos(psfPeakPos, psfWidth))
var py = float64(ypos(psfPeakPos, psfWidth))
var diffx uint64 = uint64(rx - px)
var diffy uint64 = uint64(ry - py)
var startx = math.Max(0, float64(rx-px))
var starty = math.Max(0, float64(ry-py))
var stopx = math.Min(float64(residualWidth-1), rx+(float64(psfWidth)-px-1))
var stopy = math.Min(float64(residualWidth-1), ry+(float64(psfWidth)-py-1))
factor := gain * absPeakVal
for y := uint64(starty); y <= uint64(stopy); y++ {
for x := uint64(startx); x <= uint64(stopx); x++ {
residual[posToIdx(residualWidth, x, y)] -= factor *
psf[posToIdx(psfWidth, x-diffx, y-diffy)]
}
}
}
func (driver *MesosSchedulerDriver) doReliableRegistration(maxBackoff float64) {
for {
if !driver.registerOnce() {
return
}
maxBackoff = math.Min(maxBackoff, registrationRetryIntervalMax)
// If failover timeout is present, bound the maximum backoff
// by 1/10th of the failover timeout.
if driver.failoverTimeout > 0 {
maxBackoff = math.Min(maxBackoff, driver.failoverTimeout/10.0)
}
// Determine the delay for next attempt by picking a random
// duration between 0 and 'maxBackoff' (jitter).
delay := time.Duration(maxBackoff * rand.Float64())
log.V(1).Infof("will retry registration in %v if necessary", delay)
t := time.NewTimer(delay)
defer t.Stop()
select {
case <-driver.stopCh:
return
case <-t.C:
maxBackoff *= 2
}
}
}
func extractImage(image *C.struct__VipsImage, o Options) (*C.struct__VipsImage, error) {
var err error = nil
inWidth := int(image.Xsize)
inHeight := int(image.Ysize)
switch {
case o.Crop:
width := int(math.Min(float64(inWidth), float64(o.Width)))
height := int(math.Min(float64(inHeight), float64(o.Height)))
left, top := calculateCrop(inWidth, inHeight, o.Width, o.Height, o.Gravity)
left, top = int(math.Max(float64(left), 0)), int(math.Max(float64(top), 0))
image, err = vipsExtract(image, left, top, width, height)
break
case o.Embed:
left, top := (o.Width-inWidth)/2, (o.Height-inHeight)/2
image, err = vipsEmbed(image, left, top, o.Width, o.Height, o.Extend)
break
case o.Top > 0 || o.Left > 0:
if o.AreaWidth == 0 {
o.AreaHeight = o.Width
}
if o.AreaHeight == 0 {
o.AreaHeight = o.Height
}
if o.AreaWidth == 0 || o.AreaHeight == 0 {
return nil, errors.New("Extract area width/height params are required")
}
image, err = vipsExtract(image, o.Left, o.Top, o.AreaWidth, o.AreaHeight)
break
}
return image, err
}
// startingStepSize implements the algorithm for estimating the starting step
// size as described in:
// - Hairer, E., Wanner, G., Nørsett, S.: Solving Ordinary Differential
// Equations I: Nonstiff Problems. Springer Berlin Heidelberg (1993)
func startingStepSize(rhs Function, init, tmp *State, weight Weighting, w []float64, order float64, s *Settings) float64 {
// Store 1 / (rtol * |Y_i| + atol) into w.
weight(init.Y, w)
d0 := s.Norm(init.Y, w)
d1 := s.Norm(init.YDot, w)
var h0 float64
if math.Min(d0, d1) < 1e-5 {
h0 = 1e-6
} else {
// Make the increment of an explicit Euler step small compared to the
// size of the initial value.
h0 = 0.01 * d0 / d1
}
// Perform one explicit Euler step.
floats.AddScaledTo(tmp.Y, init.Y, h0, init.YDot)
// Evaluate the right-hand side f(init.Time+h, tmp.Y).
rhs(tmp.YDot, init.Time+h0, tmp.Y)
// Estimate the second derivative of the solution.
floats.Sub(tmp.YDot, init.YDot)
d2 := s.Norm(tmp.YDot, w) / h0
var h1 float64
if math.Max(d1, d2) < 1e-15 {
h1 = math.Max(1e-6, 1e-3*h0)
} else {
h1 = math.Pow(0.01/math.Max(d1, d2), 1/(order+1))
}
return math.Min(100*h0, h1)
}
// generateValidatedLengthExample generates a random size array of examples based on what's given.
func (eg *exampleGenerator) generateValidatedLengthExample() interface{} {
minlength, maxlength := math.Inf(1), math.Inf(-1)
for _, v := range eg.a.Validations {
switch actual := v.(type) {
case *dslengine.MinLengthValidationDefinition:
minlength = math.Min(minlength, float64(actual.MinLength))
maxlength = math.Max(maxlength, float64(actual.MinLength))
case *dslengine.MaxLengthValidationDefinition:
minlength = math.Min(minlength, float64(actual.MaxLength))
maxlength = math.Max(maxlength, float64(actual.MaxLength))
}
}
count := 0
if math.IsInf(minlength, 1) {
count = int(maxlength) - (eg.r.Int() % 3)
} else if math.IsInf(maxlength, -1) {
count = int(minlength) + (eg.r.Int() % 3)
} else if minlength < maxlength {
count = int(minlength) + (eg.r.Int() % int(maxlength-minlength))
} else if minlength == maxlength {
count = int(minlength)
} else {
panic("Validation: MinLength > MaxLength")
}
if !eg.a.Type.IsArray() {
return eg.r.faker.Characters(count)
}
res := make([]interface{}, count)
for i := 0; i < count; i++ {
res[i] = eg.a.Type.ToArray().ElemType.GenerateExample(eg.r)
}
return res
}
func (self *Population) evaluate() {
for k := 0; k < self.conf.CrossoversCount; k++ {
if rand.Float64() < self.conf.CrossoverProb {
g1 := self.P[rand.Int31n(int32(math.Min(float64(len(self.P)), float64(self.conf.SelectionCount))))]
g2 := self.P[rand.Int31n(int32(math.Min(float64(len(self.P)), float64(self.conf.SelectionCount))))]
child := g1.Crossover(g2)
if rand.Float64() < self.conf.MutationProb {
child.Mutate()
}
child.EvalFitness()
self.P = append(self.P, child)
}
}
self.sort()
if self.conf.RemoveDuplicates {
self.removeDuplicates()
}
for i := range self.P {
self.P[i].EvalFitness()
}
if len(self.P) > self.conf.PopulationSize {
self.P = self.P[:self.conf.PopulationSize]
}
// pretty.Println(self.P)
}
// stepMovingObj steps the specified MovingObj and draws its image to its new position onto the LabImg.
func stepMovingObj(m *model.MovingObj) {
x, y := int(m.Pos.X), int(m.Pos.Y)
// Only horizontal or vertical movement is allowed!
if x != m.TargetPos.X {
dx := math.Min(dt*model.V, math.Abs(float64(m.TargetPos.X)-m.Pos.X))
if x > m.TargetPos.X {
dx = -dx
m.Direction = model.DirLeft
} else {
m.Direction = model.DirRight
}
m.Pos.X += dx
} else if y != m.TargetPos.Y {
dy := math.Min(dt*model.V, math.Abs(float64(m.TargetPos.Y)-m.Pos.Y))
if y > m.TargetPos.Y {
dy = -dy
m.Direction = model.DirUp
} else {
m.Direction = model.DirDown
}
m.Pos.Y += dy
}
// Draw image at new position
m.DrawImg()
}
func (pm *ProjectileManager) CheckCollision(p pM.Projectiler, dx, dy float64) (bool, gameObjectsBase.Activer) {
center := p.GetCenter()
newCenter := geometry.MakePoint(center.X+dx, center.Y+dy)
rects := make([]*geometry.Rectangle, 0, 100)
rect2obj := make(map[*geometry.Rectangle]gameObjectsBase.Activer)
for i := int(math.Min(center.Y, newCenter.Y)); i <= int(math.Max(center.Y, newCenter.Y)); i++ {
for j := int(math.Min(center.X, newCenter.X)); j <= int(math.Max(center.X, newCenter.X)); j++ {
if pm.field.IsBlocked(j, i) {
rects = append(rects, pm.field.GetCellRectangle(j, i))
} else {
for _, actor := range pm.field.GetActors(j, i) {
r := actor.GetRectangle()
rects = append(rects, &r)
rect2obj[&r] = actor
}
}
}
}
s := geometry.MakeSegment(center.X, center.Y, center.X+dx, center.Y+dy)
for _, rect := range rects {
if rect.CrossedBySegment(s) {
return true, rect2obj[rect]
}
}
return false, nil
}
func GeoCell(lat, lon float64, resolution int) string {
north := 90.0
south := -90.0
east := 180.0
west := -180.0
cell := make([]byte, resolution, resolution)
for i := 0; i < resolution; i++ {
subcellLonSpan := (east - west) / GEOCELL_GRID_SIZE
subcellLatSpan := (north - south) / GEOCELL_GRID_SIZE
x := int(math.Min(GEOCELL_GRID_SIZE*(lon-west)/(east-west), GEOCELL_GRID_SIZE-1))
y := int(math.Min(GEOCELL_GRID_SIZE*(lat-south)/(north-south), GEOCELL_GRID_SIZE-1))
pos := (y&2)<<2 | (x&2)<<1 | (y&1)<<1 | (x&1)<<0
cell[i] = GEOCELL_ALPHABET[pos]
south += subcellLatSpan * float64(y)
north = south + subcellLatSpan
west += subcellLonSpan * float64(x)
east = west + subcellLonSpan
}
return string(cell)
}
// RGBToHSV converts an RGB triple to a HSV triple.
//
// Ported from http://goo.gl/Vg1h9
func RGBToHSV(r, g, b uint8) (h, s, v float64) {
fR := float64(r) / 255
fG := float64(g) / 255
fB := float64(b) / 255
max := math.Max(math.Max(fR, fG), fB)
min := math.Min(math.Min(fR, fG), fB)
d := max - min
s, v = 0, max
if max > 0 {
s = d / max
}
if max == min {
// Achromatic.
h = 0
} else {
// Chromatic.
switch max {
case fR:
h = (fG - fB) / d
if fG < fB {
h += 6
}
case fG:
h = (fB-fR)/d + 2
case fB:
h = (fR-fG)/d + 4
}
h /= 6
}
return
}
// Expand returns a bounding box that holds both bounding box and a vector.
func (b BB) Expand(v Vect) BB {
return BB{
math.Min(b.l, v.X),
math.Min(b.b, v.Y),
math.Max(b.r, v.X),
math.Max(b.t, v.Y)}
}
func recursive(string1, string2 string) float64 {
if len(string1) == 0 {
return float64(len(string2))
}
if len(string2) == 0 {
return float64(len(string1))
}
if (len(string2) == 0) && (len(string1) == 0) {
return 0.0
}
mismatch_1 := recursive(string1, string2[0:len(string2)-1]) + 1.0
mismatch_2 := recursive(string1[0:len(string1)-1], string2) + 1.0
var cost float64
if string1[len(string1)-1] == string2[len(string2)-1] {
cost = 0.0
} else {
cost = 1.0
}
mismatch_3 := recursive(string1[0:len(string1)-1], string2[0:len(string2)-1]) + cost
return math.Min(math.Min(mismatch_1, mismatch_2), mismatch_3)
}
// Merge returns a bounding box that holds both bounding boxes.
func (a BB) Merge(b BB) BB {
return BB{
math.Min(a.l, b.l),
math.Min(a.b, b.b),
math.Max(a.r, b.r),
math.Max(a.t, b.t)}
}
func (b *Microfacet) G(wo, wi, wh *Vector) float64 {
NdotWh := AbsCosTheta(wh)
NdotWo := AbsCosTheta(wo)
NdotWi := AbsCosTheta(wi)
WOdotWh := AbsDotVector(wo, wh)
return math.Min(1.0, math.Min((2.0*NdotWh*NdotWo/WOdotWh), (2.0*NdotWh*NdotWi/WOdotWh)))
}
//uses local absolute path, generates metadata for file
func createFileMeta(path string, f os.FileInfo) (bt bt_file, err error) {
d, err := ioutil.ReadFile(path)
if err != nil {
return bt, err
}
fmt.Println(f.Size())
//TODO compute this smarter, not just min(256k, len(file))
plength := int(math.Min(float64(PIECE_LENGTH), float64(f.Size())))
if plength == 0 {
return bt, err
}
iters := len(d) / plength
if len(d)%plength > 0 {
iters += 1
}
//compute sha1 of each piece
var wg sync.WaitGroup
pieces := make([]byte, 0, iters*20)
wg.Add(iters)
for i := 0; i < iters; i++ {
go func(i int) {
s := sha1.Sum(d[plength*i : int(math.Min(float64(plength*(i+1)), float64(len(d))))])
pieces = append(pieces[:i*20], append(s[:], pieces[i*20:]...)...)
wg.Done()
}(i)
}
wg.Wait()
return bt_file{f.ModTime().Unix(), f.Size(), plength, string(pieces)}, nil
}
func (p *Paginator) Pages() []int {
if p.pageRange == nil && p.nums > 0 {
var pages []int
pageNums := p.PageNums()
page := p.Page()
switch {
case page >= pageNums-4 && pageNums > 9:
start := pageNums - 9 + 1
pages = make([]int, 9)
for i, _ := range pages {
pages[i] = start + i
}
case page >= 5 && pageNums > 9:
start := page - 5 + 1
pages = make([]int, int(math.Min(9, float64(page+4+1))))
for i, _ := range pages {
pages[i] = start + i
}
default:
pages = make([]int, int(math.Min(9, float64(pageNums))))
for i, _ := range pages {
pages[i] = i + 1
}
}
p.pageRange = pages
}
return p.pageRange
}
// RGBToHSL converts an RGB triple to a HSL triple.
//
// Ported from http://goo.gl/Vg1h9
func RGBToHSL(r, g, b uint8) (h, s, l float64) {
fR := float64(r) / 255
fG := float64(g) / 255
fB := float64(b) / 255
max := math.Max(math.Max(fR, fG), fB)
min := math.Min(math.Min(fR, fG), fB)
l = (max + min) / 2
if max == min {
// Achromatic.
h, s = 0, 0
} else {
// Chromatic.
d := max - min
if l > 0.5 {
s = d / (2.0 - max - min)
} else {
s = d / (max + min)
}
switch max {
case fR:
h = (fG - fB) / d
if fG < fB {
h += 6
}
case fG:
h = (fB-fR)/d + 2
case fB:
h = (fR-fG)/d + 4
}
h /= 6
}
return
}
func cellIDFromFaceIJWrap(f, i, j int) CellID {
// Convert i and j to the coordinates of a leaf cell just beyond the
// boundary of this face. This prevents 32-bit overflow in the case
// of finding the neighbors of a face cell.
i = clamp(i, -1, maxSize)
j = clamp(j, -1, maxSize)
// We want to wrap these coordinates onto the appropriate adjacent face.
// The easiest way to do this is to convert the (i,j) coordinates to (x,y,z)
// (which yields a point outside the normal face boundary), and then call
// xyzToFaceUV to project back onto the correct face.
//
// The code below converts (i,j) to (si,ti), and then (si,ti) to (u,v) using
// the linear projection (u=2*s-1 and v=2*t-1). (The code further below
// converts back using the inverse projection, s=0.5*(u+1) and t=0.5*(v+1).
// Any projection would work here, so we use the simplest.) We also clamp
// the (u,v) coordinates so that the point is barely outside the
// [-1,1]x[-1,1] face rectangle, since otherwise the reprojection step
// (which divides by the new z coordinate) might change the other
// coordinates enough so that we end up in the wrong leaf cell.
const scale = 1.0 / maxSize
limit := math.Nextafter(1, 2)
u := math.Max(-limit, math.Min(limit, scale*float64((i<<1)+1-maxSize)))
v := math.Max(-limit, math.Min(limit, scale*float64((j<<1)+1-maxSize)))
// Find the leaf cell coordinates on the adjacent face, and convert
// them to a cell id at the appropriate level.
f, u, v = xyzToFaceUV(faceUVToXYZ(f, u, v))
return cellIDFromFaceIJ(f, stToIJ(0.5*(u+1)), stToIJ(0.5*(v+1)))
}
func RectsIntersection(r1, r2 Rect) (ri Rect) {
ri.Min.X = math.Max(r1.Min.X, r2.Min.X)
ri.Min.Y = math.Max(r1.Min.Y, r2.Min.Y)
ri.Max.X = math.Min(r1.Max.X, r2.Max.X)
ri.Max.Y = math.Min(r1.Max.Y, r2.Max.Y)
return
}
func (v3 *Vector3) Clamp(min, max *Vector3) *Vector3 {
v3.X = math.Max(min.X, math.Min(max.X, v3.X))
v3.Y = math.Max(min.Y, math.Min(max.Y, v3.Y))
v3.Z = math.Max(min.Z, math.Min(max.Z, v3.Z))
return v3
}
func (p *Pagination) Pages(maxShowPages int) []int {
if maxShowPages < 5 || maxShowPages > MAX_SHOW_PAGE {
maxShowPages = MAX_SHOW_PAGE
}
middlePageNum := maxShowPages / 2
if p.pageRange == nil && p.Total > 0 {
var pages []int
pageNums := p.TotalPages()
page := p.Page
switch {
case page >= pageNums-middlePageNum && pageNums > maxShowPages:
start := pageNums - maxShowPages + 1
pages = make([]int, maxShowPages)
for i := range pages {
pages[i] = start + i
}
case page >= (middlePageNum+1) && pageNums > maxShowPages:
start := page - middlePageNum
pages = make([]int, int(math.Min(float64(maxShowPages), float64(page+middlePageNum+1))))
for i := range pages {
pages[i] = start + i
}
default:
pages = make([]int, int(math.Min(float64(maxShowPages), float64(pageNums))))
for i := range pages {
pages[i] = i + 1
}
}
p.pageRange = pages
}
return p.pageRange
}
func (b *Bounds) ExtendPoint(point Point) *Bounds {
b.Min.X = math.Min(b.Min.X, point.X)
b.Min.Y = math.Min(b.Min.Y, point.Y)
b.Max.X = math.Max(b.Max.X, point.X)
b.Max.Y = math.Max(b.Max.Y, point.Y)
return b
}
// GetStringBounds returns the approximate pixel bounds of the string s at x, y.
// The left edge of the em square of the first character of s
// and the baseline intersect at 0, 0 in the returned coordinates.
// Therefore the top and left coordinates may well be negative.
func (gc *ImageGraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
font, err := gc.loadCurrentFont()
if err != nil {
log.Println(err)
return 0, 0, 0, 0
}
top, left, bottom, right = 10e6, 10e6, -10e6, -10e6
cursor := 0.0
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := font.Index(rune)
if hasPrev {
cursor += fUnitsToFloat64(font.Kerning(int32(gc.Current.Scale), prev, index))
}
if err := gc.glyphBuf.Load(gc.Current.Font, int32(gc.Current.Scale), index, truetype.NoHinting); err != nil {
log.Println(err)
return 0, 0, 0, 0
}
e0 := 0
for _, e1 := range gc.glyphBuf.End {
ps := gc.glyphBuf.Point[e0:e1]
for _, p := range ps {
x, y := pointToF64Point(p)
top = math.Min(top, y)
bottom = math.Max(bottom, y)
left = math.Min(left, x+cursor)
right = math.Max(right, x+cursor)
}
}
cursor += fUnitsToFloat64(font.HMetric(int32(gc.Current.Scale), index).AdvanceWidth)
prev, hasPrev = index, true
}
return left, top, right, bottom
}
func (b *Bounds) ExtendPointZM(pointZM PointZM) *Bounds {
b.Min.X = math.Min(b.Min.X, pointZM.X)
b.Min.Y = math.Min(b.Min.Y, pointZM.Y)
b.Max.X = math.Max(b.Max.X, pointZM.X)
b.Max.Y = math.Max(b.Max.Y, pointZM.Y)
return b
}
// fast nearest-neighbor resize, no filtering
func resizeNearest(src *image.NRGBA, width, height int) *image.NRGBA {
dstW, dstH := width, height
srcBounds := src.Bounds()
srcW := srcBounds.Max.X
srcH := srcBounds.Max.Y
dst := image.NewNRGBA(image.Rect(0, 0, dstW, dstH))
dx := float64(srcW) / float64(dstW)
dy := float64(srcH) / float64(dstH)
Parallel(dstH, func(partStart, partEnd int) {
for dstY := partStart; dstY < partEnd; dstY++ {
fy := (float64(dstY)+0.5)*dy - 0.5
for dstX := 0; dstX < dstW; dstX++ {
fx := (float64(dstX)+0.5)*dx - 0.5
srcX := int(math.Min(math.Max(math.Floor(fx+0.5), 0.0), float64(srcW)))
srcY := int(math.Min(math.Max(math.Floor(fy+0.5), 0.0), float64(srcH)))
srcOff := srcY*src.Stride + srcX*4
dstOff := dstY*dst.Stride + dstX*4
copy(dst.Pix[dstOff:dstOff+4], src.Pix[srcOff:srcOff+4])
}
}
})
return dst
}