Initial checkin
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Stefan Haustein
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1 changed files with 301 additions and 0 deletions
301
src/main/java/TerminalImageViewer.java
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301
src/main/java/TerminalImageViewer.java
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import java.awt.Graphics2D;
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import java.awt.image.BufferedImage;
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import java.io.File;
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import java.io.IOException;
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import java.net.URL;
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import java.util.Arrays;
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import javax.imageio.ImageIO;
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public class TerminalImageViewer {
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/**
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* Main method, handles command line arguments and loads and scales images.
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*/
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public static void main(String[] args) throws IOException {
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if (args.length == 0) {
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System.out.println("Image file name required. Use -w to set the width in characters (default: 80).");
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return;
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}
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int w = 80 * 4;
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for (int i = 0; i < args.length; i++) {
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String name = args[i];
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if (name.equals("-w")) {
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w = 4 * Integer.parseInt(args[++i]);
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continue;
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}
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BufferedImage original;
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if (name.startsWith("http://") || name.startsWith("https://")) {
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URL url = new URL(name);
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original = ImageIO.read(url);
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} else {
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original = ImageIO.read(new File(args[0]));
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}
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int ow = original.getWidth();
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int oh = original.getHeight();
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int h = oh * w / ow;
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BufferedImage image = original;
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if (w != ow) {
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image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
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Graphics2D graphics = image.createGraphics();
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graphics.drawImage(original, 0, 0, w, h, null);
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}
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ImageData imageData = new ImageData(w, h);
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byte[] data = imageData.data;
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int[] rgbArray = new int[w];
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for (int y = 0; y < image.getHeight(); y++) {
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image.getRGB(0, y, image.getWidth(), 1, rgbArray, 0, w);
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int pos = y * w * 4;
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for (int x = 0; x < w; x++) {
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int rgb = rgbArray[x];
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data[pos++] = (byte) (rgb >> 16);
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data[pos++] = (byte) (rgb >> 8);
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data[pos++] = (byte) rgb;
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pos++;
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}
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}
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System.out.println(imageData.dump());
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}
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}
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/**
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* ANSI control code helpers
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*/
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static class Ansi {
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public static final String RESET = "\u001b[0m";
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public static String fgColor(int r, int g, int b) {
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return "\u001b[38;2;" + (r & 255) + ";" + (g & 255) + ";" + (b & 255) + "m";
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}
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public static String bgColor(int r, int g, int b) {
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return "\u001b[48;2;" + (r & 255) + ";" + (g & 255) + ";" + (b & 255) + "m";
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}
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}
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/**
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* Converts 4x8 RGB pixel to a unicode character and a foreground and background character.
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* Uses a variation of the median cut algorithm to determine a two-color palette for the
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* character, then creates a corresponding bitmap for the partial image covered by the
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* character and finds the best match in the character bitmap table.
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*/
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static class BlockChar {
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/**
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* Assumed bitmaps of the supported characters
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*/
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static int[] BITMAPS = new int[] {
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0x00000000, ' ',
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0x000ff000, '\u2501',
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0x000cc000, '\u2578',
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0x00033000, '\u257a',
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0xffff0000, '\u2580', // upper 1/2
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0x0000000f, '\u2581', // lower 1/8
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0x000000ff, '\u2582', // lower 1/4
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0x00000fff, '\u2583',
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0x0000ffff, '\u2584', // lower 1/2
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0x000fffff, '\u2585',
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0x00ffffff, '\u2586', // lower 3/4
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0x0fffffff, '\u2587',
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0xffffffff, '\u2588', // full
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0xeeeeeeee, '\u258a', // left 3/4
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0xcccccccc, '\u258c', // left 1/2
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0x88888888, '\u258e', // left 1/4
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0x0000cccc, '\u2596', // quadrant lower left
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0x00003333, '\u2597', // quadrant lower right
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0xcccc0000, '\u2598', // quadrant upper left
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0xccccffff, '\u2599', // ...
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0xcccc3333, '\u259a',
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0xffffcccc, '\u259b',
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0xffff3333, '\u259c',
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0x33330000, '\u259d',
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0x3333cccc, '\u259e',
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0x3333ffff, '\u259f',
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0x0006ff60, '\u25cf', // Black circle
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0x000137f0, '\u25e2', // Triangles
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0x0008cef0, '\u25e3',
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0x000fec80, '\u25e4',
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0x000f7310, '\u25e5'
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};
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/** Minimum value for each color channel. */
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int[] min = new int[3];
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/** Maximum value for each color channel. */
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int[] max = new int[3];
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/** Red, green and blue components of the selected background color. */
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int[] bgColor = new int[3];
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/** Red, green and blue components of the selected background color. */
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int[] fgColor = new int[3];
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/** The selected character. */
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char character;
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/**
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* Converts a set of pixels to a unicode character and a background and foreground color.
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* data contains the rgba values, p0 is the start point in data and scanWidth the number
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* of bytes in each row of data.
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*/
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void load(byte[] data, int p0, int scanWidth) {
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Arrays.fill(min, 255);
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Arrays.fill(max, 0);
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Arrays.fill(bgColor, 0);
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Arrays.fill(fgColor, 0);
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// Determine the minimum and maximum value for each color channel
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int pos = p0;
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for (int y = 0; y < 8; y++) {
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for (int x = 0; x < 4; x++) {
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for (int i = 0; i < 3; i++) {
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int d = data[pos++] & 255;
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min[i] = Math.min(min[i], d);
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max[i] = Math.max(max[i], d);
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}
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pos++; // Alpha
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}
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pos += scanWidth - 16;
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}
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// Determine the color channel with the greatest range.
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int splitIndex = 0;
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int bestSplit = 0;
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for (int i = 0; i < 3; i++) {
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if (max[i] - min[i] > bestSplit) {
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bestSplit = max[i] - min[i];
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splitIndex = i;
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}
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}
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// We just split at the middle of the interval instead of computing the median.
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int splitValue = min[splitIndex] + bestSplit / 2;
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// Compute a bitmap using the given split and sum the color values for both buckets.
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int bits = 0;
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int fgCount = 0;
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int bgCount = 0;
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pos = p0;
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for (int y = 0; y < 8; y++) {
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for (int x = 0; x < 4; x++) {
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bits = bits << 1;
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int[] avg;
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if ((data[pos + splitIndex] & 255) > splitValue) {
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avg = fgColor;
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bits |= 1;
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fgCount++;
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} else {
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avg = bgColor;
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bgCount++;
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}
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for (int i = 0; i < 3; i++) {
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avg[i] += data[pos++] & 255;
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}
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pos++; // Alpha
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}
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pos += scanWidth - 16;
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}
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// Calculate the average color value for each bucket
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for (int i = 0; i < 3; i++) {
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if (bgCount != 0) {
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bgColor[i] /= bgCount;
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}
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if (fgCount != 0) {
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fgColor[i] /= fgCount;
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}
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}
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// Find the best bitmap match by counting the bits that don't match, including
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// the inverted bitmaps.
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int bestDiff = Integer.MAX_VALUE;
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boolean invert = false;
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for (int i = 0; i < BITMAPS.length; i += 2) {
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int diff = Integer.bitCount(BITMAPS[i] ^ bits);
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if (diff < bestDiff) {
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character = (char) BITMAPS[i + 1];
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bestDiff = diff;
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invert = false;
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}
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diff = Integer.bitCount((~BITMAPS[i]) ^ bits);
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if (diff < bestDiff) {
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character = (char) BITMAPS[i + 1];
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bestDiff = diff;
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invert = true;
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}
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}
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// If the match is quite bad, use a shade image instead.
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if (bestDiff > 12) {
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invert = false;
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character = " \u2591\u2592\u2593\u2588".charAt(Math.min(4, fgCount * 5 / 32));
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}
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// If we use an inverted character, we need to swap the colors.
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if (invert) {
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int[] tmp = bgColor;
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bgColor = fgColor;
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fgColor = tmp;
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}
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}
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}
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/**
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* Roughly modeled after the corresponding HTML 5 class.
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*/
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static class ImageData {
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public final int width;
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public final int height;
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public final byte[] data;
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public ImageData(int width, int height) {
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this.width = width;
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this.height = height;
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this.data = new byte[width * height * 4];
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}
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/**
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* Convert the image to an Ansi control character string setting the colors
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*/
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public String dump() {
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StringBuilder sb = new StringBuilder();
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BlockChar blockChar = new BlockChar();
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for (int y = 0; y < height - 7; y += 8) {
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int pos = y * width * 4;
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String lastFg = "";
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String lastBg = "";
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for (int x = 0; x < width - 3; x += 4) {
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blockChar.load(data, pos, width * 4);
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String fg = Ansi.fgColor(blockChar.fgColor[0], blockChar.fgColor[1], blockChar.fgColor[2]);
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String bg = Ansi.bgColor(blockChar.bgColor[0], blockChar.bgColor[1], blockChar.bgColor[2]);
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if (!fg.equals(lastFg)) {
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sb.append(fg);
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lastFg = fg;
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}
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if (!bg.equals(lastBg)) {
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sb.append(bg);
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lastBg = bg;
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}
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sb.append(blockChar.character);
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pos += 16;
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}
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sb.append(Ansi.RESET).append("\n");
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}
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return sb.toString();
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}
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}
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}
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