/**
* Creates the Euclidian Distance Map of a (binary) byte image.
*
* @param ip The input image, not modified; must be a ByteProcessor.
* @param backgroundValue Pixels in the input with this value are interpreted as background. Note:
* for pixel value 255, write either -1 or (byte)255.
* @param edgesAreBackground Whether out-of-image pixels are considered background
* @return The EDM, containing the distances to the nearest background pixel. Returns null if the
* thread is interrupted.
*/
public FloatProcessor makeFloatEDM(
ImageProcessor ip, int backgroundValue, boolean edgesAreBackground) {
int width = ip.getWidth();
int height = ip.getHeight();
FloatProcessor fp = new FloatProcessor(width, height);
byte[] bPixels = (byte[]) ip.getPixels();
float[] fPixels = (float[]) fp.getPixels();
final int progressInterval = 100;
int nProgressUpdates =
height
/ progressInterval; // how often the progress bar is updated when passing once through y
// range
double progressAddendum = (nProgressUpdates > 0) ? 0.5 / nProgressUpdates : 0;
for (int i = 0; i < width * height; i++)
if (bPixels[i] != backgroundValue) fPixels[i] = Float.MAX_VALUE;
int[][] pointBufs =
new int[2][width]; // two buffers for two passes; low short contains x, high short y
int yDist = Integer.MAX_VALUE; // this value is used only if edges are not background
// pass 1 & 2: increasing y
for (int x = 0; x < width; x++) {
pointBufs[0][x] = NO_POINT;
pointBufs[1][x] = NO_POINT;
}
for (int y = 0; y < height; y++) {
if (edgesAreBackground) yDist = y + 1; // distance to nearest background point (along y)
edmLine(bPixels, fPixels, pointBufs, width, y * width, y, backgroundValue, yDist);
if (y % progressInterval == 0) {
if (Thread.currentThread().isInterrupted()) return null;
addProgress(progressAddendum);
}
}
// pass 3 & 4: decreasing y
for (int x = 0; x < width; x++) {
pointBufs[0][x] = NO_POINT;
pointBufs[1][x] = NO_POINT;
}
for (int y = height - 1; y >= 0; y--) {
if (edgesAreBackground) yDist = height - y;
edmLine(bPixels, fPixels, pointBufs, width, y * width, y, backgroundValue, yDist);
if (y % progressInterval == 0) {
if (Thread.currentThread().isInterrupted()) return null;
addProgress(progressAddendum);
}
}
fp.sqrt();
return fp;
} // public FloatProcessor makeFloatEDM
