private void equalizationToolStripMenuItem_Click(object sender, EventArgs e)
{
HistogramBitmap newBmp = ContrastStretch.HistogramEqualize(imgSrc);
pictureBox1.BackgroundImage = newBmp.GetBitmap();;
histogramPanel2.SetHistogram(newBmp.GetHistograms()[0]);
}
private void linear2ToolStripMenuItem_Click(object sender, EventArgs e)
{
HistogramBitmap newBmp = ContrastStretch.TwoPercentLinear(imgSrc);
pictureBox1.BackgroundImage = newBmp.GetBitmap();;
histogramPanel2.SetHistogram(newBmp.GetHistograms()[0]);
}
public static HistogramBitmap TwoPercentLinear(HistogramBitmap bmp)
{
List <Histogram> histograms = bmp.GetHistograms();
int totalSamples = 0;
for (int i = 0; i < 256; i++)
{
totalSamples += histograms[0].freqs[i];
}
int twoPercent = (int)(totalSamples * 0.02);
int botVal = histograms[0].GetLowFrequencyBin();
int topVal = histograms[0].GetHighFrequencyBin();
int cnt = 0;
while (cnt < twoPercent)
{
cnt += (int)histograms[0].freqs[botVal];
botVal++;
}
botVal--;
cnt = 0;
while (cnt < twoPercent)
{
cnt += histograms[0].freqs[topVal];
topVal--;
}
double range = topVal - botVal;
Bitmap newBmp = new Bitmap(bmp.GetBitmap());
BitmapData bmpData = newBmp.LockBits(new Rectangle(0, 0, newBmp.Width, newBmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
{
byte *imgPtr = (byte *)(bmpData.Scan0);
for (int i = 0; i < bmpData.Height; i++)
{
for (int j = 0; j < bmpData.Width; j++)
{
imgPtr[0] = Convert.ToByte(Bound(0, 255, Math.Round((imgPtr[0] - botVal) / range * 255.0)));
imgPtr[1] = Convert.ToByte(Bound(0, 255, Math.Round((imgPtr[1] - botVal) / range * 255.0)));
imgPtr[2] = Convert.ToByte(Bound(0, 255, Math.Round((imgPtr[2] - botVal) / range * 255.0)));
imgPtr += 3;
}
imgPtr += bmpData.Stride - bmpData.Width * 3;
}
}
newBmp.UnlockBits(bmpData);
return(new HistogramBitmap(newBmp));
}
private void openToolStripMenuItem_Click_1(object sender, EventArgs e)
{
if (ofd.ShowDialog() == DialogResult.OK)
{
try
{
Bitmap bmp = new Bitmap(ofd.FileName);
imgSrc = new HistogramBitmap(bmp);
pictureBox1.BackgroundImage = bmp;
List <Histogram> histograms = imgSrc.GetHistograms();
histogramPanel1.SetHistogram(histograms[0]);
histogramPanel2.SetHistogram(histograms[0]);
}
catch (Exception exc)
{
MessageBox.Show(exc.Message);
}
}
}
public static HistogramBitmap SimpleLinearStretch(HistogramBitmap img)
{
Bitmap newBmp = new Bitmap(img.GetBitmap());
// Find scale
List <Histogram> lHistograms = img.GetHistograms();
List <int> lMinVals = new List <int>();
List <double> lRanges = new List <double>();
for (int i = 0; i < img.GetNumBands(); i++)
{
int minVal = lHistograms[i].GetLowFrequencyBin();
lRanges.Add(lHistograms[i].GetHighFrequencyBin() - minVal);
lMinVals.Add(minVal);
}
// Stretch pixel values
BitmapData bmpData = newBmp.LockBits(new Rectangle(0, 0, newBmp.Width, newBmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
{
byte *imgPtr = (byte *)(bmpData.Scan0);
for (int i = 0; i < bmpData.Height; i++)
{
for (int j = 0; j < bmpData.Width; j++)
{
for (int k = 0; k < img.GetNumBands(); k++)
{
imgPtr[0] = Convert.ToByte(Math.Round((imgPtr[0] - lMinVals[k]) / lRanges[k] * 255.0));
imgPtr++;
}
}
imgPtr += bmpData.Stride - bmpData.Width * img.GetNumBands();
}
}
newBmp.UnlockBits(bmpData);
HistogramBitmap newImg = new HistogramBitmap(newBmp);
return(newImg);
}
public static HistogramBitmap HistogramEqualize(HistogramBitmap bmp)
{
Bitmap newBmp = new Bitmap(bmp.GetBitmap());
// Cumulative distribution function
int[] cdfsR = new int[256];
int[] cdfsG = new int[256];
int[] cdfsB = new int[256];
// Calculate cumulative distribution function
int cdfR = 0;
int cdfG = 0;
int cdfB = 0;
for (int i = 0; i < 256; i++)
{
if (bmp.GetHistograms()[0].freqs[i] != 0)
{
cdfR += bmp.GetHistograms()[0].freqs[i];
cdfsR[i] = cdfR;
}
if (bmp.GetHistograms()[1].freqs[i] != 0)
{
cdfG += bmp.GetHistograms()[1].freqs[i];
cdfsG[i] = cdfG;
}
if (bmp.GetHistograms()[2].freqs[i] != 0)
{
cdfB += bmp.GetHistograms()[2].freqs[i];
cdfsB[i] = cdfB;
}
}
// Find min cdfs
int cdfRMin = int.MaxValue;
int cdfGMin = int.MaxValue;
int cdfBMin = int.MaxValue;
for (int i = 0; i < 256; i++)
{
cdfRMin = Math.Min(cdfRMin, cdfsR[i]);
cdfGMin = Math.Min(cdfGMin, cdfsG[i]);
cdfBMin = Math.Min(cdfBMin, cdfsB[i]);
}
double rSize = bmp.GetBitmap().Height *bmp.GetBitmap().Width - cdfRMin;
double gSize = bmp.GetBitmap().Height *bmp.GetBitmap().Width - cdfGMin;
double bSize = bmp.GetBitmap().Height *bmp.GetBitmap().Width - cdfBMin;
// Equalize pixel values
BitmapData bmpData = newBmp.LockBits(new Rectangle(0, 0, newBmp.Width, newBmp.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
unsafe
{
byte *imgPtr = (byte *)(bmpData.Scan0);
for (int i = 0; i < bmpData.Height; i++)
{
for (int j = 0; j < bmpData.Width; j++)
{
double valR = Bound(0, 255, Math.Round((cdfsR[imgPtr[0]] - cdfRMin) / rSize * 255.0));
double valG = Bound(0, 255, Math.Round((cdfsG[imgPtr[1]] - cdfGMin) / gSize * 255.0));
double valB = Bound(0, 255, Math.Round((cdfsB[imgPtr[2]] - cdfRMin) / bSize * 255.0));
imgPtr[0] = Convert.ToByte(valR);
imgPtr[1] = Convert.ToByte(valG);
imgPtr[2] = Convert.ToByte(valB);
imgPtr += 3;
}
imgPtr += bmpData.Stride - bmpData.Width * 3;
}
}
newBmp.UnlockBits(bmpData);
return(new HistogramBitmap(newBmp));
}
