/** Sets a rectangle inside the image with the specified value. */
public static void fillRectangle(
ImageInt8 img, int value, int x0, int y0, int width, int height) {
int x1 = x0 + width;
int y1 = y0 + height;
for (int y = y0; y < y1; y++) {
for (int x = x0; x < x1; x++) {
if (img.isInBounds(x, y)) img.set(x, y, value);
}
}
}
/**
* Fills the whole image with the specified pixel value
*
* @param img An image.
* @param value The value that the image is being filled with.
*/
public static void fill(ImageInt8 img, int value) {
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++) {
data[index++] = (byte) value;
}
}
}
/**
* Computes the mean squared error (MSE) between the two images.
*
* @param imgA first image. Not modified.
* @param imgB second image. Not modified.
* @return error between the two images.
*/
public static double computeMeanSquaredError(ImageInt8 imgA, ImageInt8 imgB) {
final int h = imgA.getHeight();
final int w = imgA.getWidth();
double total = 0;
for (int y = 0; y < h; y++) {
for (int x = 0; x < w; x++) {
double difference = imgA.get(x, y) - imgB.get(x, y);
total += difference * difference;
}
}
return total / (w * h);
}
/**
* Sets each value in the image to a value drawn from an uniform distribution that has a range of
* min <= X < max.
*/
public static void randomize(ImageInt8 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++) {
data[index++] = (byte) (rand.nextInt(range) + min);
}
}
}
/** Flips the image from top to bottom */
public static void flipVertical(ImageInt8 img) {
int h2 = img.height / 2;
for (int y = 0; y < h2; y++) {
int index1 = img.getStartIndex() + y * img.getStride();
int index2 = img.getStartIndex() + (img.height - y - 1) * img.getStride();
int end = index1 + img.width;
while (index1 < end) {
int tmp = img.data[index1];
img.data[index1++] = img.data[index2];
img.data[index2++] = (byte) tmp;
}
}
}
