/*
* 1位深度图像 颜色表数组255个元素 只有用前两个 0对应0 1对应255
* 1位深度图像每个像素占一位
* 8位深度图像每个像素占一个字节 是1位的8倍
*/
/// <summary>
/// 将源灰度图像二值化，并转化为1位二值图像。
/// </summary>
/// <param name="bmp"> 源灰度图像。 </param>
/// <returns> 1位二值图像。 </returns>
public static BitmapImage GTo2Bit(BitmapImage bitmapImage)
{
if (bitmapImage != null)
{
Bitmap bitmap = HelpClass.BitmapImage2Bitmap(bitmapImage);
//将源图像内存区域锁定
Rectangle rect = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
BitmapData bitmapData = bitmap.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format8bppIndexed);
//获取图像参数
int leng, offset_1bit = 0;
int width = bitmapData.Width;
int height = bitmapData.Height;
int stride = bitmapData.Stride; //扫描线的宽度，比实际图片要大
int offset = stride - width; //显示宽度与扫描线宽度的间隙
IntPtr ptr = bitmapData.Scan0; //获取bitmapData的内存起始位置的指针
int scanBytesLength = stride * height; //用stride宽度，表示这是内存区域的大小
if (width % 32 == 0)
{
leng = width / 8;
}
else
{
leng = width / 8 + (4 - (width / 8 % 4));
if (width % 8 != 0)
{
offset_1bit = leng - width / 8;
}
else
{
offset_1bit = leng - width / 8;
}
}
//分别设置两个位置指针，指向源数组和目标数组
int posScan = 0, postDst = 0;
byte[] rgbValues = new byte[scanBytesLength]; //为目标数组分配内存
Marshal.Copy(ptr, rgbValues, 0, scanBytesLength); //将图像数据拷贝到rgbValues中
//分配二值数组
byte[] grayValues = new byte[leng * height]; //不含未用空间
//计数二值数组
int x, v, t = 0;
for (int i = 0; i < height; i++)
{
for (x = 0; x < width; x++)
{
v = rgbValues[posScan];
t = (t << 1) | (v > 100 ? 1 : 0);
if (x % 8 == 7)
{
grayValues[posScan] = (byte)t;
postDst++;
t = 0;
}
posScan++;
}
if ((x %= 8) != 7)
{
t <<= 8 - x;
grayValues[postDst] = (byte)t;
}
//跳过图像数据每行未用空间的字节，length=stride-width*bytePerPixel
posScan += offset;
postDst += offset_1bit;
}
//内存解锁
Marshal.Copy(rgbValues, 0, ptr, scanBytesLength);
bitmap.UnlockBits(bitmapData);
//构建1位二值位图
Bitmap retBitmap = two(grayValues, width, height);
return(HelpClass.Bitmap2BitmapImage(retBitmap));
}
else
{
return(null);
}
}
//Otsu阈值
public static BitmapImage OtsuThreshold(BitmapImage bitmapImage)
{
Bitmap bitmap = HelpClass.BitmapImage2Bitmap(bitmapImage);
//图像灰度化
// bitmap = Gray(bitmap);
int width = bitmap.Width;
int height = bitmap.Height;
byte threshold = 0;
int[] hist = new int[256];
int AllPixelNumber = 0, PixelNumberSmall = 0, PixelNumberBig = 0;
double MaxValue, AllSum = 0, SumSmall = 0, SumBig, ProbabilitySmall, ProbabilityBig, Probability;
BitmapData data = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
unsafe
{
byte *p = (byte *)data.Scan0;
int offset = data.Stride - width * 4;
for (int j = 0; j < height; j++)
{
for (int i = 0; i < width; i++)
{
hist[p[0]]++;
p += 4;
}
p += offset;
}
bitmap.UnlockBits(data);
}
//计算灰度为I的像素出现的概率
for (int i = 0; i < 256; i++)
{
AllSum += i * hist[i]; //质量矩
AllPixelNumber += hist[i]; //质量
}
MaxValue = -1.0;
for (int i = 0; i < 256; i++)
{
PixelNumberSmall += hist[i];
PixelNumberBig = AllPixelNumber - PixelNumberSmall;
if (PixelNumberBig == 0)
{
break;
}
SumSmall += i * hist[i];
SumBig = AllSum - SumSmall;
ProbabilitySmall = SumSmall / PixelNumberSmall;
ProbabilityBig = SumBig / PixelNumberBig;
Probability = PixelNumberSmall * ProbabilitySmall * ProbabilitySmall + PixelNumberBig * ProbabilityBig * ProbabilityBig;
if (Probability > MaxValue)
{
MaxValue = Probability;
threshold = (byte)i;
}
}
return(HelpClass.Bitmap2BitmapImage(Thresholding(bitmap, threshold)));
}
