Floyd-Steinberg抖动算法简直量身为价签这种低颜色呈现设备准备的。由于价签的墨水屏能够呈现的色彩非常有限，根据型号不同，有的只能显示黑白，有的只能显示黑白红，有的只能显示黑白黄，所以对于一张普通图片，需要将其转换为两色或者三色才能比较好地在价签上展示出来。

核心代码如下：

public class BMPConverter {public static RGBTriple[] getPalette(int deviceType) {final RGBTriple[] palette;if (deviceType == 0) {//黑白价签palette = new RGBTriple[]{new RGBTriple(0, 0, 0),new RGBTriple(255, 255, 255)};} else if (deviceType == 1) {//黑白红价签palette = new RGBTriple[]{new RGBTriple(0, 0, 0),new RGBTriple(255, 255, 255),new RGBTriple(255, 0, 0)};} else {//黑白黄价签palette = new RGBTriple[]{new RGBTriple(0, 0, 0),new RGBTriple(255, 255, 255),new RGBTriple(255, 255, 0)};}return palette;}public static byte[][] floydSteinbergDither(RGBTriple[][] image, RGBTriple[] palette){byte[][] result = new byte[image.length][image[0].length];for (int y = 0; y < image.length; y++) {for (int x = 0; x < image[y].length; x++) {RGBTriple currentPixel = image[y][x];byte index = findNearestColor(currentPixel, palette);result[y][x] = index;for (int i = 0; i < 3; i++){int error = (currentPixel.channels[i] & 0xff) - (palette[index].channels[i] & 0xff);if (x + 1 < image[0].length) {image[y+0][x+1].channels[i] =plus_truncate_uchar(image[y+0][x+1].channels[i], (error*7) >> 4);}if (y + 1 < image.length) {if (x - 1 > 0) {image[y+1][x-1].channels[i] =plus_truncate_uchar(image[y+1][x-1].channels[i], (error*3) >> 4);}image[y+1][x+0].channels[i] =plus_truncate_uchar(image[y+1][x+0].channels[i], (error*5) >> 4);if (x + 1 < image[0].length) {image[y+1][x+1].channels[i] =plus_truncate_uchar(image[y+1][x+1].channels[i], (error*1) >> 4);}}}}}return result;}private static byte plus_truncate_uchar(byte a, int b) {if ((a & 0xff) + b < 0) {return 0;} else if ((a & 0xff) + b > 255) {return (byte) 255;} else {return (byte) (a + b);}}private static byte findNearestColor(RGBTriple color, RGBTriple[] palette) {int minDistanceSquared = 255*255 + 255*255 + 255*255 + 1;byte bestIndex = 0;for (byte i = 0; i < palette.length; i++) {int Rdiff = (color.channels[0] & 0xff) - (palette[i].channels[0] & 0xff);int Gdiff = (color.channels[1] & 0xff) - (palette[i].channels[1] & 0xff);int Bdiff = (color.channels[2] & 0xff) - (palette[i].channels[2] & 0xff);int distanceSquared = Rdiff*Rdiff + Gdiff*Gdiff + Bdiff*Bdiff;if (distanceSquared < minDistanceSquared) {minDistanceSquared = distanceSquared;bestIndex = i;}}return bestIndex;}}public class  RGBTriple {public final byte[] channels;public RGBTriple() { channels = new byte[3]; }public RGBTriple(int R, int G, int B){ channels = new byte[]{(byte)R, (byte)G, (byte)B}; }
}

原始图片：

黑白红价签的显示效果：

黑白价签的显示效果：