diff options
| -rw-r--r-- | go.mod | 2 | ||||
| -rw-r--r-- | integralimg.go | 111 |
2 files changed, 6 insertions, 107 deletions
@@ -1 +1,3 @@ module rescribe.xyz/integralimg + +go 1.14 diff --git a/integralimg.go b/integralimg.go index f952c56..53aec13 100644 --- a/integralimg.go +++ b/integralimg.go @@ -1,4 +1,4 @@ -// Copyright 2019 Nick White. +// Copyright 2020 Nick White. // Use of this source code is governed by the GPLv3 // license that can be found in the LICENSE file. @@ -15,9 +15,9 @@ // integral := integralimg.NewImage(b) // draw.Draw(integral, b, img, b.Min, draw.Src) // -// This package also defines a Window, which is a rectangular -// section of an integral image. This has several methods to do -// useful calculations on the part of the image represented. +// The Sum(), Mean() and MeanStdDev() functions provided for the +// integral versions of Images significantly speed up many common +// image processing operations. package integralimg import ( @@ -184,15 +184,6 @@ 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. @@ -204,97 +195,3 @@ func MeanStdDev(i Image, sq SqImage, r image.Rectangle) (float64, float64) { return imean, math.Sqrt(variance) } - -// Window is a section of an Integral Image -type Window struct { - topleft uint64 - topright uint64 - bottomleft uint64 - bottomright uint64 - width int - height int -} - -// GetWindow gets the values of the corners of a square part of an -// Integral Image, plus the dimensions of the part, which can -// be used to quickly calculate the mean of the area -func (i Image) GetWindow(x, y, size int) Window { - step := size / 2 - - minx, miny := 0, 0 - maxy := i.Bounds().Dy() - 1 - maxx := i.Bounds().Dx() - 1 - - if y > (step+1) { - miny = y - step - 1 - } - if x > (step+1) { - minx = x - step - 1 - } - - if maxy > (y + step) { - maxy = y + step - } - if maxx > (x + step) { - maxx = x + step - } - - return Window { i[miny][minx], i[miny][maxx], i[maxy][minx], i[maxy][maxx], maxx-minx, maxy-miny} -} - -func (i SqImage) GetWindow(x, y, size int) Window { - return Image(i).GetWindow(x, y, size) -} - -// GetVerticalWindow gets the values of the corners of a vertical -// slice of an Integral Image, starting at x -func (i Image) GetVerticalWindow(x, width int) Window { - maxy := i.Bounds().Dy() - 1 - xbound := i.Bounds().Dx() - 1 - maxx := x + width - if maxx > xbound { - maxx = xbound - } - - return Window { i[0][x], i[0][maxx], i[maxy][x], i[maxy][maxx], width, maxy } -} - -func (i SqImage) GetVerticalWindow(x, width int) Window { - return Image(i).GetVerticalWindow(x, width) -} - -// Sum returns the sum of all pixels in a Window -func (w Window) Sum() uint64 { - return w.bottomright + w.topleft - w.topright - w.bottomleft -} - -// Size returns the total size of a Window -func (w Window) Size() int { - return w.width * w.height -} - -// Mean returns the average value of pixels in a Window -func (w Window) Mean() float64 { - return float64(w.Sum()) / float64(w.Size()) -} - -// Proportion returns the proportion of pixels which are on -func (w Window) Proportion() float64 { - area := w.width * w.height - // 1 << 16 - 1 as we're using Gray16, so for a binarised - // image then 1 << 16 - 1 = on - sum := float64(w.Sum()) / float64(1 << 16 - 1) - return float64(area) / float64(sum) - 1 -} - -// MeanStdDevWindow calculates the mean and standard deviation of -// a section on an Integral Image, using the corresponding Square -// Integral Image. -func MeanStdDevWindow(i Image, sq SqImage, x, y, size int) (float64, float64) { - imean := i.GetWindow(x, y, size).Mean() - smean := sq.GetWindow(x, y, size).Mean() - - variance := smean - (imean * imean) - - return imean, math.Sqrt(variance) -} |