/// <summary>
/// Gets the sum of the areas of the rectangular features in an integral image
/// </summary>
/// <param name="image"></param>
/// <param name="x"></param>
/// <param name="y"></param>
/// <returns></returns>
public double GetSum(ImageHelper image, int x, int y)
{
double sum = 0.0;
if (!Tilted)
{
// Compute the sum for a standard feature
foreach (RectangleHelper rect in Rectangles)
{
sum += image.GetSum(x + rect.scaledX, y + rect.scaledY,
rect.scaledWidth, rect.scaledHeight) * rect.scaledWeight;
}
}
else
{
// Compute the sum for a rotated feature
foreach (RectangleHelper rect in Rectangles)
{
sum += image.GetSumT(x + rect.scaledX, y + rect.scaledY,
rect.scaledWidth, rect.scaledHeight) * rect.scaledWeight;
}
}
return sum;
}
/// <summary>
/// This is where we do the detection for an image passing in the interest window
/// </summary>
/// <param name="pImage"></param>
/// <param name="pWindow"></param>
/// <returns></returns>
public bool Compute(ImageHelper pImage, Rectangle pWindow)
{
// grab the dimensions
int x = pWindow.X;
int y = pWindow.Y;
int w = pWindow.Width;
int h = pWindow.Height;
// figure out the details of the window in the image
double mean = pImage.GetSum(x, y, w, h) * invArea;
double factor = pImage.GetSum2(x, y, w, h) * invArea - (mean * mean);
// do the math to adjust the factor
factor = (factor >= 0) ? Math.Sqrt(factor) : 1;
// For each classification stage in the cascade
foreach (Stage stage in cascade.stages)
{
// Check to see if the image was rejected
if (stage.Classify(pImage, x, y, factor) == false)
{
return false; // If it was, we tell the caller that we were rejected.
}
}
// If we've gone through all the stages and were not rejected, the object was detected inside the window
return true;
}
/// <summary>
/// Constructor passing in an unmanaged image, a channel, and the flag to compute a tilted image
/// </summary>
/// <param name="pImage"></param>
/// <param name="pChannel"></param>
/// <param name="pComputeTilted"></param>
/// <returns></returns>
public static ImageHelper FromBitmap(AForge.Imaging.UnmanagedImage pImage, int pChannel, bool pComputeTilted)
{
// check image format, we'll have the same issue with bitmaps here as we did before
if (!(pImage.PixelFormat == PixelFormat.Format8bppIndexed ||
pImage.PixelFormat == PixelFormat.Format24bppRgb ||
pImage.PixelFormat == PixelFormat.Format32bppArgb))
{
throw new AForge.Imaging.UnsupportedImageFormatException("Only grayscale and 24 bpp RGB images are supported.");
}
// find the pixel size
int pixelSize = System.Drawing.Image.GetPixelFormatSize(pImage.PixelFormat) / 8;
// get source image size
int pWidth = pImage.Width;
int pHeight = pImage.Height;
int pStride = pImage.Stride;
int pOffset = pStride - pWidth * pixelSize;
// create integral image
ImageHelper im = new ImageHelper(pWidth, pHeight, pComputeTilted);
int* nSum = im.intImage, sSum = im.squaredImage, tSum = im.tiltedImage;
// compute the adjusted widths and heights for the other two operations
int nWidth = im.nWidth, nHeight = im.nHeight;
int tWidth = im.tWidth, tHeight = im.tHeight;
// We're going to have an issue if the channel doesn't support 8 bpp
if (pImage.PixelFormat == PixelFormat.Format8bppIndexed && pChannel != 0)
throw new ArgumentException("Only the first channel is available for 8 bpp images.", "channel");
// grab the image pointer src
byte* srcStart = (byte*)pImage.ImageData.ToPointer() + pChannel;
// do the job
byte* src = srcStart;
// for each line
for (int y = 1; y <= pHeight; y++)
{
int yy = nWidth * (y);
int y1 = nWidth * (y - 1);
// for each pixel
for (int x = 1; x <= pWidth; x++, src += pixelSize)
{
// set p1 to the src
// and square it for p2
int p1 = *src;
int p2 = p1 * p1;
// find the indexes for each sum
int r = yy + (x);
int a = yy + (x - 1);
int b = y1 + (x);
int c = y1 + (x - 1);
// and sum them up!
nSum[r] = p1 + nSum[a] + nSum[b] - nSum[c];
sSum[r] = p2 + sSum[a] + sSum[b] - sSum[c];
}
src += pOffset;
}
// if we're computing the tilted image as well, there is a lot more going on
if (pComputeTilted)
{
// grab the source
src = srcStart;
// Left-to-right, top-to-bottom pass
for (int y = 1; y <= pHeight; y++, src += pOffset)
{
// compute the new yy and y1
int yy = tWidth * (y);
int y1 = tWidth * (y - 1);
for (int x = 2; x < pWidth + 2; x++, src += pixelSize)
{
// find the indexes
int a = y1 + (x - 1);
int b = yy + (x - 1);
int c = y1 + (x - 2);
int r = yy + (x);
// and sum them up
tSum[r] = *src + tSum[a] + tSum[b] - tSum[c];
}
}
{
int yy = tWidth * (pHeight);
int y1 = tWidth * (pHeight + 1);
for (int x = 2; x < pWidth + 2; x++, src += pixelSize)
{
int a = yy + (x - 1);
int c = yy + (x - 2);
int b = y1 + (x - 1);
int r = y1 + (x);
tSum[r] = tSum[a] + tSum[b] - tSum[c];
}
}
// Now do it Right-to-left, and bottom-to-top
for (int y = pHeight; y >= 0; y--)
{
// compute the new values
int yy = tWidth * (y);
int y1 = tWidth * (y + 1);
for (int x = pWidth + 1; x >= 1; x--)
{
// grab the indexes
int r = yy + (x);
int b = y1 + (x - 1);
// and add them up
tSum[r] += tSum[b];
}
}
for (int y = pHeight + 1; y >= 0; y--)
{
// grab the new value
int yy = tWidth * (y);
for (int x = pWidth + 1; x >= 2; x--)
{
// compute the indexes
int r = yy + (x);
int b = yy + (x - 2);
// and add them up
tSum[r] -= tSum[b];
}
}
}
// finally return the restult... All the math should be done by this point
return im;
}
/// <summary>
/// Classifies an image as having the searched object or not.
/// </summary>
public bool Classify(ImageHelper pImage, int row, int column, double pFactor)
{
// Keep track of how close to the threshold we are.
double achievedThreshold = 0;
// For each feature in the feature tree of the current stage,
foreach (FeatureNode[] node in nodes)
{
int current = 0;
do
{
// Get the feature node from the current branch in the node tree
FeatureNode feature = node[current];
// Evaluate the node's feature
double sum = feature.mFeature.GetSum(pImage, row, column);
// And increase the value accumulator
if (sum < feature.mThreshold * pFactor)
{
achievedThreshold += feature.mLeftValue;
current = feature.mLeft;
}
else
{
achievedThreshold += feature.mRightValue;
current = feature.mRight;
}
} while (current > 0);
}
// If the achieved threshold is greater than the desired threshold we have found a face!!
if (achievedThreshold <= this.threshold)
{
// Otherwise our image doesn't contain what we're looking for.
return false;
}
else
{
// We had a match!
return true;
}
}
