/// <summary>
/// Contrast the image (Contrast by expanding the histogram on all channel)
/// </summary>
/// <param name="source">The image to be Contrasted</param>
/// <returns>The image Contrasted</returns>
protected override IImageAdapter ProcessFilter(IImageAdapter source)
{
// Check Params
if (source == null)
{
throw new ArgumentNullException("source", "Argument cannot be null");
}
IImageAdapter retVal = new ImageAdapter(source.Width, source.Height);
int[] min = new int[] { (int)source[0, 0].MinChannelValue, (int)source[0, 0].MinChannelValue, (int)source[0, 0].MinChannelValue, (int)source[0, 0].MinChannelValue };
int[] max = new int[] { (int)source[0, 0].MaxChannelValue, (int)source[0, 0].MaxChannelValue, (int)source[0, 0].MaxChannelValue, (int)source[0, 0].MaxChannelValue };
Hashtable dico = IPUtil.BuildHistogram(source);
Hashtable stretched = new Hashtable();
for (int channel = 1; channel < IPUtil.intColor.Length; channel++) // Ignore Alpha Channel
{
ArrayList[] list = new ArrayList[256];
for (int index = 0; index < 256; index++)
{
list[index] = new ArrayList();
}
stretched.Add(IPUtil.intColor[channel], list);
}
stretched[IPUtil.ALPHA] = ((ArrayList[])dico[IPUtil.ALPHA]).Clone(); // Clone Alpha channel from original Histogram
// Find the min and max value of the histogram
for (int channel = 1; channel < IPUtil.intColor.Length; channel++) // ignore the alpha channel
{
bool minFound = false;
ArrayList[] array = (ArrayList[])dico[IPUtil.intColor[channel]];
for (int index = 0; index < 256; index++)
{
if (array[index].Count != 0)
{
max[channel] = index;
minFound = true;
}
else
{
if (!minFound)
{
min[channel] = index;
}
}
}
}
// Stretch the histogram
// Transformation used :
// (min <= i <= max)
// Stretch : (i - min) * 255 / ( max - min) + 0.5
for (int channel = 1; channel < IPUtil.intColor.Length; channel++) // Ignore the Alpha Channel
{
ArrayList[] channelOriginal = (ArrayList[])dico[IPUtil.intColor[channel]];
ArrayList[] channelStretched = (ArrayList[])stretched[IPUtil.intColor[channel]];
int minChannel = min[channel];
int maxChannel = max[channel];
float stretchConstant = (float)source[0, 0].NormalizedValue / (float)(maxChannel - minChannel);
float stretch = 0f;
for (int index = minChannel; index <= maxChannel; index++)
{
stretch = (index - minChannel) * stretchConstant + 0.5f;
channelStretched[(int)stretch].AddRange(channelOriginal[index]);
}
}
retVal = IPUtil.HistogramToIImageAdapter(stretched, source);
dico.Clear();
stretched.Clear();
return(retVal);
}
/// <summary>
/// Equalize the image (Equalize the histogram on all channel, except alpha)
/// (build and use the histogram of the image to do so)
/// </summary>
/// <param name="source">The image to be equalized</param>
/// <returns>The image equalized</returns>
protected override IImageAdapter ProcessFilter(IImageAdapter source)
{
// Check params
if (source == null)
{
throw new ArgumentNullException("source", "Argument cannot be null");
}
int[] sum = new int[] { 0, 0, 0, 0 };
Hashtable equalized = new Hashtable();
Hashtable dico = IPUtil.BuildHistogram(source);
IImageAdapter retVal = new ImageAdapter(source.Width, source.Height);
// Init HashTable -- contains 4 ArrayList[] : 4 channels of 256 entries ( ArrayList of points )
for (int channel = 1; channel < IPUtil.intColor.Length; channel++) // Ignore Alpha Channel
{
ArrayList[] list = new ArrayList[256];
for (int index = 0; index < 256; index++)
{
list[index] = new ArrayList();
}
equalized.Add(IPUtil.intColor[channel], list);
}
equalized[IPUtil.ALPHA] = ((ArrayList[])dico[IPUtil.ALPHA]).Clone(); // Clone Alpha channel from original Histogram
// compute the sum per channel
for (int channel = 0; channel < IPUtil.intColor.Length; channel++)
{
ArrayList[] array = (ArrayList[])dico[IPUtil.intColor[channel]];
for (int index = 0; index < 256; index++)
{
sum[channel] += array[index].Count;
}
}
// Stretch and Normalize the histogram
// Transformation used :
// (min <= i <= max)
// Normalize : 0.5 + ( Sum(0,i-1) + ( Sum(i-1,i) / 2 ) ) * 255 / Sum(0,255)
for (int channel = 1; channel < IPUtil.intColor.Length; channel++) // Ignore Alpha channel
{
ArrayList[] channelOriginal = (ArrayList[])dico[IPUtil.intColor[channel]];
ArrayList[] channelEqualized = (ArrayList[])equalized[IPUtil.intColor[channel]];
float equalizeConstant = 255.0f / ((sum[channel] != 0) ? sum[channel] : 1);
int currentSum = 0;
float equalize = 0f;
for (int index = 0; index < 256; index++)
{
equalize = 0.5f + (currentSum + channelOriginal[index].Count / 2) * equalizeConstant;
currentSum += channelOriginal[index].Count;
channelEqualized[(int)equalize].AddRange(channelOriginal[index]);
}
}
retVal = IPUtil.HistogramToIImageAdapter(equalized, source);
equalized.Clear();
dico.Clear();
return(retVal);
}
