diff options
| -rw-r--r-- | integralimg.go | 82 |
1 files changed, 81 insertions, 1 deletions
diff --git a/integralimg.go b/integralimg.go index c088be4..f952c56 100644 --- a/integralimg.go +++ b/integralimg.go @@ -38,7 +38,7 @@ type SqImage [][]uint64 func (i Image) ColorModel() color.Model { return color.Gray16Model } func (i Image) Bounds() image.Rectangle { - return image.Rectangle {image.Point{0, 0}, image.Point{len(i[0]), len(i)}} + return image.Rect(0, 0, len(i[0]), len(i)) } // at64 is used to return the raw uint64 for a given pixel. Accessing @@ -125,6 +125,86 @@ func NewSqImage(r image.Rectangle) *SqImage { return &s } +func lowest(a, b int) int { + if a < b { + return a + } + return b +} + +func highest(a, b int) int { + if a > b { + return a + } + return b +} + +func (i Image) topLeft(r image.Rectangle) uint64 { + x := highest(r.Min.X, 0) + y := highest(r.Min.Y, 0) + return i[y][x] +} + +func (i Image) topRight(r image.Rectangle) uint64 { + x := lowest(r.Max.X, i.Bounds().Dx() - 1) + y := highest(r.Min.Y, 0) + return i[y][x] +} + +func (i Image) bottomLeft(r image.Rectangle) uint64 { + x := highest(r.Min.X, 0) + y := lowest(r.Max.Y, i.Bounds().Dy() - 1) + return i[y][x] +} + +func (i Image) bottomRight(r image.Rectangle) uint64 { + x := lowest(r.Max.X, i.Bounds().Dx() - 1) + y := lowest(r.Max.Y, i.Bounds().Dy() - 1) + return i[y][x] +} + +// Sum returns the sum of all pixels in a rectangle +func (i Image) Sum(r image.Rectangle) uint64 { + return i.bottomRight(r) + i.topLeft(r) - i.topRight(r) - i.bottomLeft(r) +} + +// Mean returns the average value of pixels in a rectangle +func (i Image) Mean(r image.Rectangle) float64 { + in := r.Intersect(i.Bounds()) + return float64(i.Sum(r)) / float64(in.Dx() * in.Dy()) +} + +// Sum returns the sum of all pixels in a rectangle +func (i SqImage) Sum(r image.Rectangle) uint64 { + return Image(i).Sum(r) +} + +// Mean returns the average value of pixels in a rectangle +func (i SqImage) Mean(r image.Rectangle) float64 { + return Image(i).Mean(r) +} + +// Proportion returns the proportion of pixels which are not white +func (i Image) ProportionNotWhite(r image.Rectangle) float64 { + in := r.Intersect(i.Bounds()) + area := in.Dx() * in.Dy() + // 1 << 16 - 1 as we're using Gray16, so 1 << 16 - 1 = white + sum := float64(i.Sum(r)) / float64(1 << 16 - 1) + return 1 - float64(area) / float64(sum) +} + +// MeanStdDev calculates the mean and standard deviation of a +// section of an image, using the corresponding regular and square +// integral images. +func MeanStdDev(i Image, sq SqImage, r image.Rectangle) (float64, float64) { + imean := i.Mean(r) + smean := sq.Mean(r) + + variance := smean - (imean * imean) + + return imean, math.Sqrt(variance) +} + // Window is a section of an Integral Image type Window struct { topleft uint64 |