Initial data commit

Task/Bitmap-Histogram/Java/bitmap-histogram.java

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+import java.awt.image.BufferedImage;
+import java.io.File;
+import java.io.IOException;
+import javax.imageio.ImageIO;
+
+public enum ImageProcessing {
+    ;
+
+    public static void main(String[] args) throws IOException {
+        BufferedImage img = ImageIO.read(new File("example.png"));
+
+        BufferedImage bwimg = toBlackAndWhite(img);
+
+        ImageIO.write(bwimg, "png", new File("example-bw.png"));
+    }
+
+    private static int luminance(int rgb) {
+        int r = (rgb >> 16) & 0xFF;
+        int g = (rgb >> 8) & 0xFF;
+        int b = rgb & 0xFF;
+        return (r + b + g) / 3;
+    }
+
+    private static BufferedImage toBlackAndWhite(BufferedImage img) {
+        int width = img.getWidth();
+        int height = img.getHeight();
+
+        int[] histo = computeHistogram(img);
+
+        int median = getMedian(width * height, histo);
+
+        BufferedImage bwimg = new BufferedImage(width, height, img.getType());
+        for (int y = 0; y < height; y++) {
+            for (int x = 0; x < width; x++) {
+                bwimg.setRGB(x, y, luminance(img.getRGB(x, y)) >= median ? 0xFFFFFFFF : 0xFF000000);
+            }
+        }
+        return bwimg;
+    }
+
+    private static int[] computeHistogram(BufferedImage img) {
+        int width = img.getWidth();
+        int height = img.getHeight();
+
+        int[] histo = new int[256];
+        for (int y = 0; y < height; y++) {
+            for (int x = 0; x < width; x++) {
+                histo[luminance(img.getRGB(x, y))]++;
+            }
+        }
+        return histo;
+    }
+
+    private static int getMedian(int total, int[] histo) {
+        int median = 0;
+        int sum = 0;
+        for (int i = 0; i < histo.length && sum + histo[i] < total / 2; i++) {
+            sum += histo[i];
+            median++;
+        }
+        return median;
+    }
+}