/**
* Runs a canny edge detector on the input image given the provided thresholds. If configured to
* save a list of trace points then the output image is optional.
*
* <p>NOTE: Input and output can be the same instance, if the image type allows it.
*
* @param input Input image. Not modified.
* @param threshLow Lower threshold. >= 0.
* @param threshHigh Upper threshold. >= 0.
* @param output (Might be option) Output binary image. Edge pixels are marked with 1 and
* everything else 0.
*/
public void process(T input, float threshLow, float threshHigh, ImageUInt8 output) {
if (threshLow < 0 || threshHigh < 0)
throw new IllegalArgumentException("Threshold must be >= zero!");
if (hysteresisMark != null) {
if (output == null)
throw new IllegalArgumentException(
"An output image must be specified when configured to mark edge points");
}
// setup internal data structures
blurred.reshape(input.width, input.height);
derivX.reshape(input.width, input.height);
derivY.reshape(input.width, input.height);
intensity.reshape(input.width, input.height);
suppressed.reshape(input.width, input.height);
angle.reshape(input.width, input.height);
direction.reshape(input.width, input.height);
work.reshape(input.width, input.height);
// run canny edge detector
blur.process(input, blurred);
gradient.process(blurred, derivX, derivY);
GGradientToEdgeFeatures.intensityAbs(derivX, derivY, intensity);
GGradientToEdgeFeatures.direction(derivX, derivY, angle);
GradientToEdgeFeatures.discretizeDirection4(angle, direction);
GradientToEdgeFeatures.nonMaxSuppression4(intensity, direction, suppressed);
performThresholding(threshLow, threshHigh, output);
}
/**
* Specify internal algorithms and behavior.
*
* @param blur Initial blur applied to image.
* @param gradient Computes the image gradient.
* @param saveTrace Should it save a list of points that compose the objects contour/trace?
*/
public CannyEdge(BlurFilter<T> blur, ImageGradient<T, D> gradient, boolean saveTrace) {
this.blur = blur;
this.gradient = gradient;
Class<T> imageType = blur.getInputType().getImageClass();
blurred = GeneralizedImageOps.createSingleBand(imageType, 1, 1);
derivX = gradient.getDerivativeType().createImage(1, 1);
derivY = gradient.getDerivativeType().createImage(1, 1);
if (saveTrace) {
hysteresisPts = new HysteresisEdgeTracePoints();
} else {
hysteresisMark = new HysteresisEdgeTraceMark();
}
}
@Override
protected void process(GrayU8 gray, Bitmap output, byte[] storage) {
gradient.process(gray, derivX, derivY);
VisualizeImageData.colorizeGradient(derivX, derivY, -1, output, storage);
}