我需要做直方图拉伸
我有一个 BitmapFrames 数组,需要进行直方图拉伸。我知道这与直方图均衡不同,最终结果是什么......有点。问题是我完全不知道得到直方图后该怎么做。
到目前为止,我的代码为直方图创建了一个数组,因此我知道每个值有多少个像素。但在那之后我不知道该怎么办。
这是我到目前为止的代码...现在它制作直方图,然后直方图均衡...这不是我想要的...我只是想了解有关直方图的更多信息,
[Cmdlet(VerbsData.ConvertTo, "HistoStretch")]
public class HistoStretchCmdlet : PSCmdlet
{
private BitmapFrame[] bFrame, outFrame;
private BitmapSource src;
private double pixelsize;
private byte[] pixels, outPixels;
private byte MAX_VAL;
private int[] histogram;
private int cf, start;
[Parameter(ValueFromPipeline = true,
ValueFromPipelineByPropertyName = true), ValidateNotNullOrEmpty]
public BitmapFrame[] Bitmap
{
get
{
return bFrame;
}
set
{
bFrame = value;
}
}
protected override void ProcessRecord()
{
base.ProcessRecord();
Console.Write("Applying a histogram stretch to the image...\n\n");
outFrame = new BitmapFrame[bFrame.Length];
for (int c = 0; c < bFrame.Length; c++)
{
MAX_VAL = (byte)((1 << bFrame[c].Format.BitsPerPixel) - 1);
histogram = new int[MAX_VAL + 1];
for (int i = 0; i <= MAX_VAL; i++)
{
histogram[i] = 0;
}
pixelsize = bFrame[c].PixelWidth * bFrame[c].PixelHeight;
pixels = new byte[(int)pixelsize];
outPixels = new byte[(int)pixelsize];
bFrame[c].CopyPixels(pixels,(int)bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8),0);
for (int i = 0; i < pixelsize; i++)
{
histogram[(int)pixels[i]] = histogram[(int)pixels[i]] + 1;
}
for (int i = 0; i <= MAX_VAL; i++)
{
Console.Write("{0}: {1}\n", i, histogram[i]);
}
for (int i = 0; i <= MAX_VAL; i++)
{
if (histogram[i] >= 1)
{
start = i;
break;
}
}
for (int i = 0; i < pixelsize; i++)
{
cf = 0;
for (int g = 0; g <= MAX_VAL; g++)
{
cf += histogram[g];
if (g == pixels[i])
{
break;
}
}
outPixels[i] = (byte)(cf * (MAX_VAL / pixelsize));
}
src = BitmapSource.Create(bFrame[c].PixelWidth, bFrame[c].PixelHeight, bFrame[c].DpiX, bFrame[c].DpiY,
bFrame[c].Format, bFrame[c].Palette, outPixels, (int)(bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8)));
outFrame[c] = BitmapFrame.Create(src);
}
WriteObject(outFrame);
}
}
这就是直方图应该是什么样子据我的老师说:
http://www.fileden.com /files/2009/8/18/2547657/histostretch.PNG
我运行了上面的代码......并得到了一个直黑色图像。 这是我的代码:
outFrame = new BitmapFrame[bFrame.Length];
for (int c = 0; c < bFrame.Length; c++)
{
MAX_VAL = (byte)((1 << bFrame[c].Format.BitsPerPixel) - 1);
histogram = new int[MAX_VAL + 1];
for (int i = 0; i <= MAX_VAL; i++)
{
histogram[i] = 0;
}
pixelsize = bFrame[c].PixelWidth * bFrame[c].PixelHeight;
pixels = new byte[(int)pixelsize];
outPixels = new byte[(int)pixelsize];
bFrame[c].CopyPixels(pixels,(int)bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8),0);
max = pixels[0];
min = pixels[0];
for (int i = 0; i < pixelsize; i++)
{
histogram[(int)pixels[i]] = histogram[(int)pixels[i]] + 1;
if((int)pixels[i] > max)
max = pixels[i];
if((int)pixels[i] < min)
min = pixels[i];
}
dynamic = max - min;
for (int i = 0; i < pixelsize; i++)
{
outPixels[i] = (byte)(((pixels[i] - min) / dynamic) * MAX_VAL);
}
I have an array of BitmapFrames and need to do a histogram stretch. I know this is different from a histogram equalization, and what the final outcome is... sorta. the problem is I have absolutely no idea what to do after I get the histogram.
So far my code creates an array for the histogram so I know how many pixels of each value i have. But after that I don't know what to do.
this is the code I have so far... right now it makes the histogram and then histogram equalizes... which is NOT what I want... I was just trying to learn more about histograms
[Cmdlet(VerbsData.ConvertTo, "HistoStretch")]
public class HistoStretchCmdlet : PSCmdlet
{
private BitmapFrame[] bFrame, outFrame;
private BitmapSource src;
private double pixelsize;
private byte[] pixels, outPixels;
private byte MAX_VAL;
private int[] histogram;
private int cf, start;
[Parameter(ValueFromPipeline = true,
ValueFromPipelineByPropertyName = true), ValidateNotNullOrEmpty]
public BitmapFrame[] Bitmap
{
get
{
return bFrame;
}
set
{
bFrame = value;
}
}
protected override void ProcessRecord()
{
base.ProcessRecord();
Console.Write("Applying a histogram stretch to the image...\n\n");
outFrame = new BitmapFrame[bFrame.Length];
for (int c = 0; c < bFrame.Length; c++)
{
MAX_VAL = (byte)((1 << bFrame[c].Format.BitsPerPixel) - 1);
histogram = new int[MAX_VAL + 1];
for (int i = 0; i <= MAX_VAL; i++)
{
histogram[i] = 0;
}
pixelsize = bFrame[c].PixelWidth * bFrame[c].PixelHeight;
pixels = new byte[(int)pixelsize];
outPixels = new byte[(int)pixelsize];
bFrame[c].CopyPixels(pixels,(int)bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8),0);
for (int i = 0; i < pixelsize; i++)
{
histogram[(int)pixels[i]] = histogram[(int)pixels[i]] + 1;
}
for (int i = 0; i <= MAX_VAL; i++)
{
Console.Write("{0}: {1}\n", i, histogram[i]);
}
for (int i = 0; i <= MAX_VAL; i++)
{
if (histogram[i] >= 1)
{
start = i;
break;
}
}
for (int i = 0; i < pixelsize; i++)
{
cf = 0;
for (int g = 0; g <= MAX_VAL; g++)
{
cf += histogram[g];
if (g == pixels[i])
{
break;
}
}
outPixels[i] = (byte)(cf * (MAX_VAL / pixelsize));
}
src = BitmapSource.Create(bFrame[c].PixelWidth, bFrame[c].PixelHeight, bFrame[c].DpiX, bFrame[c].DpiY,
bFrame[c].Format, bFrame[c].Palette, outPixels, (int)(bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8)));
outFrame[c] = BitmapFrame.Create(src);
}
WriteObject(outFrame);
}
}
this is what the histograms should look like according to my teacher:
http://www.fileden.com/files/2009/8/18/2547657/histostretch.PNG
I ran the code above... and got a straight black image.
here's my code:
outFrame = new BitmapFrame[bFrame.Length];
for (int c = 0; c < bFrame.Length; c++)
{
MAX_VAL = (byte)((1 << bFrame[c].Format.BitsPerPixel) - 1);
histogram = new int[MAX_VAL + 1];
for (int i = 0; i <= MAX_VAL; i++)
{
histogram[i] = 0;
}
pixelsize = bFrame[c].PixelWidth * bFrame[c].PixelHeight;
pixels = new byte[(int)pixelsize];
outPixels = new byte[(int)pixelsize];
bFrame[c].CopyPixels(pixels,(int)bFrame[c].Width * (bFrame[c].Format.BitsPerPixel / 8),0);
max = pixels[0];
min = pixels[0];
for (int i = 0; i < pixelsize; i++)
{
histogram[(int)pixels[i]] = histogram[(int)pixels[i]] + 1;
if((int)pixels[i] > max)
max = pixels[i];
if((int)pixels[i] < min)
min = pixels[i];
}
dynamic = max - min;
for (int i = 0; i < pixelsize; i++)
{
outPixels[i] = (byte)(((pixels[i] - min) / dynamic) * MAX_VAL);
}
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评论(3)
直方图拉伸是像素值的映射,使得:
换句话说,直方图拉伸意味着将图像数据的动态(84:153)拉伸到最大可能的动态(0:255)。
这不应该影响直方图峰值的高度,而只会影响它们的分布(在这一点上,插图有点误导)。
直方图拉伸 http://cct.rncan.gc.ca/resource /tutor/fundam/images/linstre.gif
图片来源
实际上这是您将应用于图像像素的映射(伪代码):
Histogram stretching is the mapping of pixel values such that:
In other words histogram stretching means stretching the dynamic of the image data (84:153) to the greatest possible dynamic (0:255).
This should not affect the hight of the histogram peaks, but only their spread (the illustration is a bit misleading on this point).
histogram stretch http://cct.rncan.gc.ca/resource/tutor/fundam/images/linstre.gif
Image source
In practice this is the mapping you would apply to the pixels of the image (pseudocode):
如果您可以控制相机的照明和/或增益/偏移,则可以优化它们并根据需要拉伸直方图。
If you have control over the lighting and or gain/offset of the camera, you can optimize those and stretch the histogram as you desire.
不要忘记考虑浮动。所以对dabonz413的答案稍作修改:
Don't forget to consider float. So a slight modification to dabonz413's answer: