public unsafe ImageU8 ToImageU8()
{
ImageU8 img = new ImageU8(this.Width, this.Height);
Grad * start = this.Start;
Grad * end = start + this.Length;
float max = 0;
// 找最大值
Grad *src = start;
while (src != end)
{
max = Math.Max(max, src->Value);
src++;
}
float coeff = max > 255 ? 255f / max : 0;
src = start;
Byte *dst = img.Start;
while (src != end)
{
*dst = (Byte)(coeff * src->Value);
dst++;
src++;
}
return(img);
}
public override IImage Clone()
{
ImageU8 img = new ImageU8(this.Width, this.Height);
img.CloneFrom(this);
return(img);
}
public unsafe ImageU8 ToGrayscaleImage(double rCoeff, double gCoeff, double bCoeff)
{
ImageU8 img = new ImageU8(this.Width, this.Height);
Argb32 *p = Start;
Byte * to = img.Start;
Argb32 *end = p + Length;
if (Length < 1024)
{
while (p != end)
{
*to = (Byte)(p->Red * rCoeff + p->Green * gCoeff + p->Blue * bCoeff);
p++;
to++;
}
}
else
{
int *bCache = stackalloc int[256];
int *gCache = stackalloc int[256];
int *rCache = stackalloc int[256];
const int shift = 1 << 10;
int rShift = (int)(rCoeff * shift);
int gShift = (int)(gCoeff * shift);
int bShift = shift - rShift - gShift;
int r = 0, g = 0, b = 0;
for (int i = 0; i < 256; i++)
{
bCache[i] = b;
gCache[i] = g;
rCache[i] = r;
b += bShift;
g += gShift;
r += rShift;
}
while (p != end)
{
*to = (Byte)((bCache[p->Red] + gCache[p->Green] + rCache[p->Red]) >> 10);
p++;
to++;
}
}
return(img);
}
public unsafe ImageU8 ToImageU8()
{
ImageU8 imgU8 = new ImageU8(this.Width, this.Height);
int length = imgU8.Length;
Int32 * start = this.Start;
Byte * dst = imgU8.Start;
Int32 * end = start + this.Length;
while (start != end)
{
int val = *start;
* dst = val < 0 ? (Byte)0 : (val > 255 ? (Byte)255 : (Byte)val);
start++;
dst++;
}
return(imgU8);
}
public unsafe ImageU8 CopyChannel(int channel)
{
if (channel < 0 && channel > 2)
{
throw new ArgumentOutOfRangeException("channel");
}
int length = this.Length;
Byte * start = (Byte *)this.StartIntPtr;
int size = sizeof(Rgb24);
Byte * end = start + sizeof(Rgb24) * length;
ImageU8 imgU8 = new ImageU8(this.Width, this.Height);
Byte * dst = imgU8.Start;
while (start != end)
{
*dst = start[channel];
start += size;
dst++;
}
return(imgU8);
}
/// <summary>
/// 进行中值滤波。
/// </summary>
/// <param name="medianRadius">
/// 中值滤波的核半径，不得小于1.
/// </param>
public unsafe void ApplyMedianFilter(int medianRadius)
{
if (medianRadius > 0)
{
// 进行中值滤波
using (ImageU8 copy = this.Clone() as ImageU8)
{
int size = medianRadius * 2 + 1;
int count = 0;
byte[] data = new byte[size * size];
int height = this.Height;
int width = this.Width;
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
count = 0;
for (int h = -medianRadius; h <= medianRadius; h++)
{
for (int w = -medianRadius; w <= medianRadius; w++)
{
int hh = y + h;
int ww = x + w;
if (hh >= 0 && hh < height && ww >= 0 && ww < width)
{
data[count] = copy[hh, ww];
count++;
}
}
}
Array.Sort(data, 0, count);
int m = count >> 1;
byte median = data[m];
this[y, x] = median;
}
}
}
}
}
/// <summary>
/// 使用 hilditch 算法进行细化
/// </summary>
public unsafe void Thinning(Byte foreground = 255)
{
Byte * start = this.Start;
Int32 width = this.Width;
Int32 height = this.Height;
Int32 *list = stackalloc Int32[8];
Byte background = (Byte)(255 - foreground);
Int32 length = this.Length;
using (ImageU8 mask = new ImageU8(this.Width, this.Height))
{
mask.Fill(0);
Boolean loop = true;
while (loop == true)
{
loop = false;
for (Int32 r = 1; r < height - 1; r++)
{
for (Int32 c = 1; c < width - 1; c++)
{
Byte *p = start + r * width + c;
// 条件1：p 必须是前景点
if (*p != foreground)
{
continue;
}
// p3 p2 p1
// p4 p p0
// p5 p6 p7
// list 存储的是补集，即前景点为0，背景点为1，以方便联结数的计算
FillNeighbors(p, list, width, foreground);
// 条件2：p0,p2,p4,p6 不皆为前景点
if (list[0] == 0 && list[2] == 0 && list[4] == 0 && list[6] == 0)
{
continue;
}
// 条件3: p0~p7至少两个是前景点
Int32 count = 0;
for (int i = 0; i < 8; i++)
{
count += list[i];
}
if (count > 6)
{
continue;
}
// 条件4：联结数等于1
if (DetectConnectivity(list) != 1)
{
continue;
}
// 条件5: 假设p2已标记删除，则令p2为背景，不改变p的联结数
if (mask[r - 1, c] == 1)
{
list[2] = 1;
if (DetectConnectivity(list) != 1)
{
continue;
}
list[2] = 0;
}
// 条件6: 假设p4已标记删除，则令p4为背景，不改变p的联结数
if (mask[r, c - 1] == 1)
{
list[4] = 1;
if (DetectConnectivity(list) != 1)
{
continue;
}
}
mask[r, c] = 1; // 标记删除
loop = true;
}
}
for (int i = 0; i < length; i++)
{
if (mask[i] == 1)
{
this[i] = background;
}
}
}
}
}
public unsafe void ApplyCannyEdgeDetector(double gaussianSiama = 1.4, int gaussianSize = 5, byte lowThreshold = 20, byte highThreshold = 100)
{
ImageU8 copy = this.Clone() as ImageU8;
int startX = 1;
int startY = 1;
int width = this.Width;
int height = this.Height;
int stopX = width - 1;
int stopY = height - 1;
int ww = width - 2;
int hh = height - 2;
// orientation array
byte[] orients = new byte[ww * hh];
// gradients array
float[,] gradients = new float[this.Width, this.Height];
float maxGradient = float.NegativeInfinity;
double gx, gy;
double orientation, toAngle = 180.0 / System.Math.PI;
float leftPixel = 0, rightPixel = 0;
// 第一步，Gauss 平滑
copy.ApplyGaussianBlur(gaussianSiama, gaussianSize);
byte *start = copy.Start + startX;
int o = 0;
for (int y = startY; y < stopY; y++)
{
byte *line = start + y * width;
byte *p = line;
for (int x = startX; x < stopX; x++, p++, o++)
{
gx = p[-width + 1] + p[width + 1]
- p[-width - 1] - p[width - 1]
+ 2 * (p[1] - p[-1]);
gy = p[-width - 1] + p[-width + 1]
- p[width - 1] - p[width + 1]
+ 2 * (p[-width] - p[width]);
gradients[x, y] = (float)Math.Sqrt(gx * gx + gy * gy);
if (gradients[x, y] > maxGradient)
{
maxGradient = gradients[x, y];
}
// get orientation
if (gx == 0)
{
orientation = (gy == 0) ? 0 : 90;
}
else
{
double div = gy / gx;
// handle angles of the 2nd and 4th quads
if (div < 0)
{
orientation = 180 - System.Math.Atan(-div) * toAngle;
}
// handle angles of the 1st and 3rd quads
else
{
orientation = System.Math.Atan(div) * toAngle;
}
// get closest angle from 0, 45, 90, 135 set
if (orientation < 22.5)
{
orientation = 0;
}
else if (orientation < 67.5)
{
orientation = 45;
}
else if (orientation < 112.5)
{
orientation = 90;
}
else if (orientation < 157.5)
{
orientation = 135;
}
else
{
orientation = 0;
}
}
// save orientation
orients[o] = (byte)orientation;
}
}
// STEP 3 - suppres non maximums
o = 0;
start = this.Start + startX;
for (int y = startY; y < stopY; y++)
{
byte *line = start + y * width;
byte *p = line;
// for each pixel
for (int x = startX; x < stopX; x++, p++, o++)
{
// get two adjacent pixels
switch (orients[o])
{
case 0:
leftPixel = gradients[x - 1, y];
rightPixel = gradients[x + 1, y];
break;
case 45:
leftPixel = gradients[x - 1, y + 1];
rightPixel = gradients[x + 1, y - 1];
break;
case 90:
leftPixel = gradients[x, y + 1];
rightPixel = gradients[x, y - 1];
break;
case 135:
leftPixel = gradients[x + 1, y + 1];
rightPixel = gradients[x - 1, y - 1];
break;
}
// compare current pixels value with adjacent pixels
if ((gradients[x, y] < leftPixel) || (gradients[x, y] < rightPixel))
{
*p = 0;
}
else
{
*p = (byte)(gradients[x, y] / maxGradient * 255);
}
}
}
// STEP 4 - hysteresis
start = this.Start + startX;
for (int y = startY; y < stopY; y++)
{
byte *line = start + y * width;
byte *p = line;
for (int x = startX; x < stopX; x++, p++)
{
if (*p < highThreshold)
{
if (*p < lowThreshold)
{
// non edge
*p = 0;
}
else
{
// check 8 neighboring pixels
if ((p[-1] < highThreshold) &&
(p[1] < highThreshold) &&
(p[-width - 1] < highThreshold) &&
(p[-width] < highThreshold) &&
(p[-width + 1] < highThreshold) &&
(p[width - 1] < highThreshold) &&
(p[width] < highThreshold) &&
(p[width + 1] < highThreshold))
{
*p = 0;
}
}
}
}
}
// STEP 4 将第1行，最后一行，第0列，最后1列
// 第1行
start = this.Start;
byte *end = start + width;
while (start != end)
{
*start = 0;
start++;
}
// 最后一行
start = this.Start + width * height - width;
end = start + width;
while (start != end)
{
*start = 0;
start++;
}
// 第一列和最后一列
start = this.Start;
for (int y = 0; y < height; y++, start += width)
{
start[0] = 0;
start[width - 1] = 0;
}
}
public unsafe void SkeletonizeByMidPoint(Byte foreground = 255)
{
using (ImageU8 mask = new ImageU8(this.Width, this.Height))
{
mask.Fill(0);
Int32 width = this.Width;
Int32 height = this.Height;
for (Int32 r = 0; r < height; r++)
{
Int32 lineStart = -1;
for (Int32 c = 0; c < width; c++)
{
if (this[r, c] == foreground)
{
if (lineStart == -1)
{
lineStart = c;
}
}
else
{
if (lineStart != -1)
{
mask[r, (lineStart + c) / 2] = 1;
lineStart = -1;
}
}
}
}
for (Int32 c = 0; c < width; c++)
{
Int32 lineStart = -1;
for (Int32 r = 0; r < height; r++)
{
if (this[r, c] == foreground)
{
if (lineStart == -1)
{
lineStart = r;
}
}
else
{
if (lineStart != -1)
{
mask[(lineStart + r) / 2, c] = 1;
lineStart = -1;
}
}
}
}
Byte bg = (Byte)(255 - foreground);
Int32 length = this.Length;
for (int i = 0; i < length; i++)
{
if (mask[i] == 1)
{
this[i] = foreground;
}
else
{
this[i] = bg;
}
}
}
}