/**
* 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);
}
/** Adds Gaussian/normal i.i.d noise to each pixel in the image. */
public static void addGaussian(ImageSInt8 img, Random rand, double sigma, int min, int max) {
final int h = img.getHeight();
final int w = img.getWidth();
byte[] data = img.data;
for (int y = 0; y < h; y++) {
int index = img.getStartIndex() + y * img.getStride();
for (int x = 0; x < w; x++) {
int value = (data[index]) + (int) (rand.nextGaussian() * sigma);
if (value < min) value = min;
if (value > max) value = max;
data[index++] = (byte) value;
}
}
}
/** Adds uniform i.i.d noise to each pixel in the image. Noise range is min <= X < max. */
public static void addUniform(ImageSInt8 img, Random rand, int min, int max) {
final int h = img.getHeight();
final int w = img.getWidth();
int range = max - min;
byte[] data = img.data;
for (int y = 0; y < h; y++) {
int index = img.getStartIndex() + y * img.getStride();
for (int x = 0; x < w; x++) {
int value = (data[index]) + rand.nextInt(range) + min;
if (value < -128) value = -128;
if (value > 127) value = 127;
data[index++] = (byte) value;
}
}
}