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@mcychan
mcychan authored Sep 22, 2024
1 parent 5421e1f commit 05a482d
Showing 1 changed file with 159 additions and 12 deletions.
171 changes: 159 additions & 12 deletions nQuantCpp/Otsu.cpp
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Original file line number Diff line number Diff line change
@@ -1,12 +1,14 @@
/* Otsu's Image Segmentation Method
Copyright (C) 2009 Tolga Birdal
Copyright (c) 2018 - 2021 Miller Cy Chan
Copyright (c) 2018 - 2024 Miller Cy Chan
*/

#include "stdafx.h"
#include "Otsu.h"
#include "bitmapUtilities.h"
#include "GilbertCurve.h"
#define _USE_MATH_DEFINES
#include <math.h>
#include <unordered_map>

namespace OtsuThreshold
Expand Down Expand Up @@ -68,7 +70,7 @@ namespace OtsuThreshold

short getOtsuThreshold(const vector<ARGB>& pixels)
{
float vet[256] = { 0 };
float vet[256] = { 0 };
int hist[256] = { 0 };

getHistogram(pixels, hist);
Expand All @@ -87,7 +89,7 @@ namespace OtsuThreshold
return findMax(vet, 256);
}

void threshold(vector<ARGB>& pixels, short thresh, float weight = 1.0f)
void threshold(const vector<ARGB>& pixels, vector<ARGB>& dest, short thresh, float weight = 1.0f)
{
auto maxThresh = (BYTE)thresh;
if (thresh >= 200)
Expand All @@ -97,16 +99,156 @@ namespace OtsuThreshold
thresh = 200;
}

auto minThresh = (BYTE)(thresh * weight);
auto minThresh = (BYTE)(thresh * weight);
for (int i = 0; i < pixels.size(); ++i) {
Color c(pixels[i]);
if (c.GetR() + c.GetG() + c.GetB() > maxThresh * 3)
pixels[i] = Color::MakeARGB(c.GetA(), BYTE_MAX, BYTE_MAX, BYTE_MAX);
if (m_transparentPixelIndex >= 0 && c.GetR() + c.GetG() + c.GetB() > maxThresh * 3)
dest[i] = Color::MakeARGB(c.GetA(), BYTE_MAX, BYTE_MAX, BYTE_MAX);
else if (m_transparentPixelIndex >= 0 || c.GetR() + c.GetG() + c.GetB() < minThresh * 3)
pixels[i] = Color::MakeARGB(c.GetA(), 0, 0, 0);
dest[i] = Color::MakeARGB(c.GetA(), 0, 0, 0);
}
}

vector<ARGB> cannyFilter(const UINT width, const vector<ARGB>& pixelsGray, double lowerThreshold, double higherThreshold) {
const auto height = pixelsGray.size() / width;
const auto area = (size_t)(width * height);

vector<ARGB> pixelsCanny(area, Color::White);

int gx[3][3] = {{-1, 0, 1}, {-2, 0, 2}, {-1, 0, 1}};
int gy[3][3] = {{-1, -2, -1}, {0, 0, 0}, {1, 2, 1}};
auto G = make_unique<double[]>(area);
vector<int> theta(area);
auto largestG = 0.0;

// perform canny edge detection on everything but the edges
for (int i = 1; i < height - 1; ++i) {
for (int j = 1; j < width - 1; ++j) {
// find gx and gy for each pixel
auto gxValue = 0.0;
auto gyValue = 0.0;
for (int x = -1; x <= 1; ++x) {
for (int y = -1; y <= 1; ++y) {
const Color c = pixelsGray[(i + x) * width + j + y];
gxValue += gx[1 - x][1 - y] * c.GetG();
gyValue += gy[1 - x][1 - y] * c.GetG();
}
}

const int center = i * width + j;
// calculate G and theta
G[center] = sqrt(pow(gxValue, 2) + pow(gyValue, 2));
auto atanResult = atan2(gyValue, gxValue) * 180.0 / M_PI;
theta[center] = (int)(180.0 + atanResult);

if (G[center] > largestG)
largestG = G[center];

// setting the edges
if (i == 1) {
G[center - 1] = G[center];
theta[center - 1] = theta[center];
}
else if (j == 1) {
G[center - width] = G[center];
theta[center - width] = theta[center];
}
else if (i == height - 1) {
G[center + 1] = G[center];
theta[center + 1] = theta[center];
}
else if (j == width - 1) {
G[center + width] = G[center];
theta[center + width] = theta[center];
}

// setting the corners
if (i == 1 && j == 1) {
G[center - width - 1] = G[center];
theta[center - width - 1] = theta[center];
}
else if (i == 1 && j == width - 1) {
G[center - width + 1] = G[center];
theta[center - width + 1] = theta[center];
}
else if (i == height - 1 && j == 1) {
G[center + width - 1] = G[center];
theta[center + width - 1] = theta[center];
}
else if (i == height - 1 && j == width - 1) {
G[center + width + 1] = G[center];
theta[center + width + 1] = theta[center];
}

// to the nearest 45 degrees
theta[center] = rint(theta[center] / 45) * 45;
}
}

largestG *= .5;

// non-maximum suppression
for (int i = 1; i < height - 1; ++i) {
for (int j = 1; j < width - 1; ++j) {
const int center = i * width + j;
if (theta[center] == 0 || theta[center] == 180) {
if (G[center] < G[center - 1] || G[center] < G[center + 1])
G[center] = 0;
}
else if (theta[center] == 45 || theta[center] == 225) {
if (G[center] < G[center + width + 1] || G[center] < G[center - width - 1])
G[center] = 0;
}
else if (theta[center] == 90 || theta[center] == 270) {
if (G[center] < G[center + width] || G[center] < G[center - width])
G[center] = 0;
}
else {
if (G[center] < G[center + width - 1] || G[center] < G[center - width + 1])
G[center] = 0;
}

auto grey = ~(BYTE)(G[center] * (255.0 / largestG));
Color c(pixelsGray[center]);
pixelsCanny[center] = Color::MakeARGB(c.GetA(), grey, grey, grey);
}
}

int k = 0;
auto minThreshold = lowerThreshold * largestG, maxThreshold = higherThreshold * largestG;
do {
for (int i = 1; i < height - 1; ++i) {
for (int j = 1; j < width - 1; ++j) {
const int center = i * width + j;
if (G[center] < minThreshold)
G[center] = 0;
else if (G[center] >= maxThreshold)
continue;
else if (G[center] < maxThreshold) {
G[center] = 0;
for (int x = -1; x <= 1; ++x) {
for (int y = -1; y <= 1; y++) {
if (x == 0 && y == 0)
continue;
if (G[center + x * width + y] >= maxThreshold) {
G[center] = higherThreshold * largestG;
k = 0;
x = 2;
break;
}
}
}
}

auto grey = ~(BYTE)(G[center] * 255.0 / largestG);
Color c(pixelsGray[center]);
pixelsCanny[center] = Color::MakeARGB(c.GetA(), grey, grey, grey);
}
}
} while (k++ < 100);
return pixelsCanny;
}

unsigned short nearestColorIndex(const ARGB* pPalette, const UINT nMaxColors, const ARGB argb, const UINT pos)
{
auto got = nearestMap.find(argb);
Expand Down Expand Up @@ -149,7 +291,7 @@ namespace OtsuThreshold
return GetARGBIndex(c, hasSemiTransparency, m_transparentPixelIndex >= 0);
}

void convertToGrayScale(vector<ARGB>& pixels)
void convertToGrayScale(const vector<ARGB>& pixels, vector<ARGB>& dest)
{
float min1 = BYTE_MAX;
float max1 = .0f;
Expand All @@ -176,7 +318,7 @@ namespace OtsuThreshold

int green = (pixels[i] >> 8) & 0xff;
auto grey = (int)((green - min1) * (BYTE_MAX / (max1 - min1)));
pixels[i] = Color::MakeARGB(alfa, grey, grey, grey);
dest[i] = Color::MakeARGB(alfa, grey, grey, grey);
}
}

Expand Down Expand Up @@ -239,7 +381,8 @@ namespace OtsuThreshold

pSourceImg->UnlockBits(&data);
return pSourceImg;
}
}


bool Otsu::ConvertGrayScaleToBinary(Bitmap* pSrcImg, Bitmap* pDest, bool isGrayscale)
{
Expand All @@ -250,11 +393,15 @@ namespace OtsuThreshold
vector<ARGB> pixels(area);
GrabPixels(pSrcImg, pixels, hasSemiTransparency, m_transparentPixelIndex, m_transparentColor, alphaThreshold);

auto pixelsGray = pixels;
if (!isGrayscale)
convertToGrayScale(pixels);
convertToGrayScale(pixels, pixelsGray);

auto oldPixels = pixels;
auto otsuThreshold = getOtsuThreshold(pixels);
threshold(pixels, otsuThreshold);
auto lowerThreshold = 0.03, higherThreshold = 0.1;
pixels = cannyFilter(bitmapWidth, pixelsGray, lowerThreshold, higherThreshold);
threshold(oldPixels, pixels, otsuThreshold);

auto pPaletteBytes = make_unique<BYTE[]>(sizeof(ColorPalette) + 2 * sizeof(ARGB));
auto pPalette = (ColorPalette*)pPaletteBytes.get();
Expand Down

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