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transform: reduce amount of calls to cos/sin #92

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Jun 14, 2022
Merged

transform: reduce amount of calls to cos/sin #92

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13 changes: 7 additions & 6 deletions transform/rotate.go
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Original file line number Diff line number Diff line change
Expand Up @@ -66,15 +66,16 @@ func Rotate(img image.Image, angle float64, options *RotationOptions) *image.RGB
angleRadians := -angle * (math.Pi / 180)

var dstW, dstH int
var sin, cos = math.Sincos(angleRadians)
if resizeBounds {
// Reserve larger size in destination image for full image bounds rotation
// If not preserving size, always take image center as pivot
pivotX, pivotY = float64(srcW)/2, float64(srcH)/2

a := math.Abs(float64(srcW) * math.Sin(angleRadians))
b := math.Abs(float64(srcW) * math.Cos(angleRadians))
c := math.Abs(float64(srcH) * math.Sin(angleRadians))
d := math.Abs(float64(srcH) * math.Cos(angleRadians))
a := math.Abs(float64(srcW) * sin)
b := math.Abs(float64(srcW) * cos)
c := math.Abs(float64(srcH) * sin)
d := math.Abs(float64(srcH) * cos)

dstW, dstH = int(c+b+0.5), int(a+d+0.5)
} else {
Expand All @@ -100,8 +101,8 @@ func Rotate(img image.Image, angle float64, options *RotationOptions) *image.RGB
for x := xStart; x < xEnd; x++ {
dx := float64(x) - pivotX + 0.5

ix := int((math.Cos(angleRadians)*dx - math.Sin(angleRadians)*dy + pivotX))
iy := int((math.Sin(angleRadians)*dx + math.Cos(angleRadians)*dy + pivotY))
ix := int((cos*dx - sin*dy + pivotX))
iy := int((sin*dx + cos*dy + pivotY))

if ix < 0 || ix >= srcW || iy < 0 || iy >= srcH {
continue
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