/// <summary>
/// 梯度给Hog单元投票
/// </summary>
/// <param name="ge">梯度</param>
public void VoteHogCell(GradientElement ge, int partnum)
{
for (int i = 0; i < partnum; i++)
{
if (ge.theta >= HistElements[i].theta && ge.theta < HistElements[i].theta + Math.PI / partnum)
{
HistElements[i].rho += ge.rho;
break;
}
}
}
/// <summary>
/// 给Hog图投票
/// </summary>
/// <param name="bmpX">投票像素点X坐标</param>
/// <param name="bmpY">投票像素点Y坐标</param>
/// <param name="ge">投票像素点梯度向量(rho, theta)</param>
private void VoteHog(int bmpX, int bmpY, GradientElement ge)
{
if (bmpX >= StartX && bmpX < StartX + HogSize.Width * CellSize.Width &&
bmpY >= StartY && bmpY < StartY + HogSize.Height * CellSize.Height)
{
int hogCellX = (bmpX - StartX) / CellSize.Width;
int hogCellY = (bmpY - StartY) / CellSize.Height;
int hogCellIndex = hogCellX + hogCellY * HogSize.Width;
HogCells[hogCellIndex].VoteHogCell(ge, PartNumber);
}
}
/// <summary>
/// 从位图（灰度图）中获取Hog图，位图像素是以从左到右、从下到上的顺序在内存中从低地址排列到高地址
/// 但是C#的Bitmap对象好像把这顺序颠倒过来了，根据实际经验发现，在BitmapData中，位图数据以从左到
/// 右、从上到下的顺序排列，和图像坐标的顺序一致
/// </summary>
/// <param name="bitmapSource">源位图</param>
/// <param name="cellHeight">单元的高度</param>
/// <param name="cellWidth">单元的宽度</param>
/// <param name="partNumber">PI弧度等分数</param>
/// <returns>Hog图</returns>
public static HogGram GetHogFromBitmap(Bitmap bitmapSource, int cellWidth, int cellHeight, int partNumber)
{
HogGram hogGram = null;
if (bitmapSource != null && bitmapSource.PixelFormat == PixelFormat.Format8bppIndexed)
{
int width = bitmapSource.Width;
int height = bitmapSource.Height;
hogGram = new HogGram(width, height, cellWidth, cellHeight, partNumber);
if (hogGram == null)
{
return(hogGram);
}
Rectangle rect = new Rectangle(0, 0, width, height);
// 获得位图内容数据
BitmapData dataSource = bitmapSource.LockBits(rect, ImageLockMode.ReadOnly, bitmapSource.PixelFormat);
// Stride为位图中每一行以4字节对齐的行宽
int strideSource = dataSource.Stride;
unsafe
{
byte *ptrSource = (byte *)dataSource.Scan0.ToPointer();
byte *ptr1 = null;
for (int row = 0; row < height; row++)
{
ptr1 = ptrSource + strideSource * row;
for (int col = 0; col < width; col++)
{
GradientElement ge = new GradientElement();
if (row == 0 || row == height - 1 || col == 0 || col == width - 1)
{
ge.rho = 0;
ge.theta = 0;
}
else
{
// 位图的在内存中的排列是从左到右，从下到上的，但BitmapData貌似做了优化，把位图数据在内存中的排列
// 顺序改为与坐标系一致，即从左到右、从上到下
double gradX = *(ptr1 + 1) - *(ptr1 - 1);
double gradY = *(ptr1 + strideSource) - *(ptr1 - strideSource);
ge.rho = Math.Sqrt(gradX * gradX + gradY * gradY);
ge.theta = Math.Atan2(gradY, gradX); // 注意坐标系是垂直翻转的
}
int bmpX = col;
int bmpY = row;
//int bmpY = height - 1 - row; // 由于BitmapData自动颠倒了位图存储序，所以这个写法是错的。
hogGram.VoteHog(bmpX, bmpY, ge);
ptr1++;
}
}
}
bitmapSource.UnlockBits(dataSource);
}
return(hogGram);
}
