import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.Range;
import org.opencv.core.Rect;
import org.opencv.core.Size;
import org.opencv.imgproc.Imgproc;
public class CLAHE {
private final static int BUFFER_SIZE = 256;
private final double clipLimit_;
private final int tilesX_;
private final int tilesY_;
Mat lut_ = new Mat();
public CLAHE() {
this(40, 8, 8);
}
public static int saturateCast(int x) {
return x > BUFFER_SIZE - 1 ? BUFFER_SIZE - 1 : (x < 0 ? 0 : x);
}
public static int saturateCast(float x) {
return (int) (x > BUFFER_SIZE - 1 ? BUFFER_SIZE - 1 : (x < 0 ? 0 : x));
}
public int GCD(int a, int b) {
return b == 0 ? a : GCD(b, a % b);
}
public CLAHE(double clipLimit, int tilesX, int tilesY) {
this.clipLimit_ = clipLimit;
this.tilesX_ = tilesX;
this.tilesY_ = tilesY;
}
public Mat apply(Mat src) {
if (src.type() != CvType.CV_8UC1) {
throw new IllegalArgumentException("Mat not of type CV_8UC1!");
}
Mat dst = new Mat(src.size(), src.type());
lut_.create(tilesX_ * tilesY_, BUFFER_SIZE, CvType.CV_8UC1);
Size tileSize;
Mat srcForLut;
if (src.cols() % tilesX_ == 0 && src.rows() % tilesY_ == 0) {
tileSize = new Size(src.cols() / tilesX_, src.rows() / tilesY_);
srcForLut = src;
} else {
Mat srcExt_ = new Mat();
Imgproc.copyMakeBorder(src, srcExt_, 0, tilesY_ - (src.rows() % tilesY_), 0, tilesX_ - (src.cols() % tilesX_), Imgproc.BORDER_REFLECT_101);
tileSize = new Size(srcExt_.cols() / tilesX_, srcExt_.rows() / tilesY_);
srcForLut = srcExt_;
}
double tileSizeTotal = tileSize.area(); // int ?
float lutScale = (float) ((BUFFER_SIZE - 1) / tileSizeTotal); // why BUFFER_SIZE - 1 ?
int clipLimit = 0;
if (clipLimit_ > 0.0) {
clipLimit = (int) (clipLimit_ * tileSizeTotal / BUFFER_SIZE);
if (clipLimit < 1) {
clipLimit = 1;
}
}
CLAHE_CalcLut_Body calcLutBody = new CLAHE_CalcLut_Body(srcForLut, lut_, tileSize, tilesX_, clipLimit, lutScale);
calcLutBody.execute(new Range(0, tilesX_ * tilesY_));
CLAHE_Interpolation_Body interpolationBody = new CLAHE_Interpolation_Body(src, dst, lut_, tileSize, tilesX_, tilesY_);
interpolationBody.execute(new Range(0, src.rows()));
return dst;
}
private class CLAHE_Interpolation_Body {
Mat src_;
Mat dst_;
Mat lut_;
Size tileSize_;
int tilesX_;
int tilesY_;
CLAHE_Interpolation_Body(Mat src, Mat dst, Mat lut_, Size tileSize, int tilesX_, int tilesY_) {
this.src_ = src;
this.dst_ = dst;
this.lut_ = lut_;
this.tileSize_ = tileSize;
this.tilesX_ = tilesX_;
this.tilesY_ = tilesY_;
}
void execute(Range range) {
int lut_step = (int) lut_.step1();
int lut_break = tilesX_ * lut_step;
for (int y = range.start; y < range.end; ++y) {
float tyf = (y / (float) tileSize_.height) - 0.5f;
int ty1 = (int) Math.floor(tyf);
int ty2 = ty1 + 1;
float ya = tyf - ty1;
// keep largest
if (ty1 < 0) {
ty1 = 0;
}
// keep smallest
if (ty2 > tilesY_ - 1) {
ty2 = tilesY_ - 1;
}
int lutPlane1 = ty1 * tilesX_;
int lutPlane2 = ty2 * tilesX_;
for (int x = 0; x < src_.cols(); x++) {
float txf = (x / (float) tileSize_.width) - 0.5f;
int tx1 = (int) Math.floor(txf);
int tx2 = tx1 + 1;
float xa = txf - tx1;
// keep largest
if (tx1 < 0) {
tx1 = 0;
}
// keep smallest
if (tx2 > tilesX_ - 1) {
tx2 = tilesX_ - 1;
}
// original pixel value
double[] ptr = src_.get(y, x);
int srcVal = (int) ptr[0];
int ind1 = tx1 * lut_step + srcVal;
int ind2 = tx2 * lut_step + srcVal;
int column1 = (ind1 + (ty1 * lut_break)) % lut_step;
int row1 = (ind1 + (ty1 * lut_break)) / lut_step;
int column2 = (ind2 + (ty1 * lut_break)) % lut_step;
int row2 = (ind2 + (ty1 * lut_break)) / lut_step;
int column3 = (ind1 + (ty2 * lut_break)) % lut_step;
int row3 = (ind1 + (ty2 * lut_break)) / lut_step;
int column4 = (ind2 + (ty2 * lut_break)) % lut_step;
int row4 = (ind2 + (ty2 * lut_break)) / lut_step;
float res = 0;
double[] lut_ptr1 = lut_.get(row1, column1);
res += ((byte) lut_ptr1[0] & 0xFF) * ((1.0f - xa) * (1.0f - ya));
double[] lut_ptr2 = lut_.get(row2, column2);
res += ((byte) lut_ptr2[0] & 0xFF) * ((xa) * (1.0f - ya));
double[] lut_ptr3 = lut_.get(row3, column3);
res += ((byte) lut_ptr3[0] & 0xFF) * ((1.0f - xa) * (ya));
double[] lut_ptr4 = lut_.get(row4, column4);
res += ((byte) lut_ptr4[0] & 0xFF) * ((xa) * (ya));
dst_.put(y, x, saturateCast(res));
}
}
}
}
private class CLAHE_CalcLut_Body {
Mat src_;
Mat lut_;
Size tileSize_;
int tilesX_;
int clipLimit_;
float lutScale_;
CLAHE_CalcLut_Body(Mat srcForLut, Mat lut_, Size tileSize, int tilesX_, int clipLimit, float lutScale) {
this.src_ = srcForLut;
this.lut_ = lut_;
this.tileSize_ = tileSize;
this.tilesX_ = tilesX_;
this.clipLimit_ = clipLimit;
this.lutScale_ = lutScale;
}
void execute(Range range) {
int[] tileHist;
int[] lutBytes = new int[lut_.height() * lut_.width()];
for (int k = range.start; k < range.end; ++k) {
int ty = k / tilesX_;
int tx = k % tilesX_;
// retrieve tile submatrix
Rect tileROI = new Rect();
tileROI.x = (int) (tx * tileSize_.width);
tileROI.y = (int) (ty * tileSize_.height);
tileROI.width = (int) tileSize_.width;
tileROI.height = (int) tileSize_.height;
Mat tile = src_.submat(tileROI);
// calc histogram
tileHist = new int[BUFFER_SIZE];
int height = tileROI.height;
for (int h = height; h > 0; h--) {
int x;
double[] ptr;
for (int w = 0; w < tileROI.width; w++) {
ptr = tile.get(h - 1, w);
tileHist[(int) ptr[0]]++;
}
}
// clip histogram
if (clipLimit_ > 0) {
// how many pixels were clipped
int clipped = 0;
for (int i = 0; i < BUFFER_SIZE; ++i) {
if (tileHist[i] > clipLimit_) {
clipped += tileHist[i] - clipLimit_;
tileHist[i] = clipLimit_;
}
}
// redistribute clipped pixels
int redistBatch = clipped / BUFFER_SIZE;
int residual = clipped - redistBatch * BUFFER_SIZE;
for (int i = 0; i < BUFFER_SIZE; ++i) {
tileHist[i] += redistBatch;
}
for (int i = 0; i < residual; ++i) {
tileHist[i]++;
}
}
// calc Lut
int sum = 0;
for (int i = 0; i < BUFFER_SIZE; ++i) {
sum += tileHist[i];
lut_.put(k, i, saturateCast(Math.round(sum * lutScale_)));
}
}
}
}
}
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