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/*
* Copyright (C) 2018 Square, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package okio.samples;
import java.io.File;
import java.io.IOException;
import okio.BufferedSink;
import okio.Okio;
public final class BitmapEncoder {
static final class Bitmap {
private final int[][] pixels;
Bitmap(int[][] pixels) {
this.pixels = pixels;
}
int width() {
return pixels[0].length;
}
int height() {
return pixels.length;
}
int red(int x, int y) {
return (pixels[y][x] & 0xff0000) >> 16;
}
int green(int x, int y) {
return (pixels[y][x] & 0xff00) >> 8;
}
int blue(int x, int y) {
return (pixels[y][x] & 0xff);
}
}
/**
* Returns a bitmap that lights up red subpixels at the bottom, green subpixels on the right, and
* blue subpixels in bottom-right.
*/
Bitmap generateGradient() {
int[][] pixels = new int[1080][1920];
for (int y = 0; y < 1080; y++) {
for (int x = 0; x < 1920; x++) {
int r = (int) (y / 1080f * 255);
int g = (int) (x / 1920f * 255);
int b = (int) ((Math.hypot(x, y) / Math.hypot(1080, 1920)) * 255);
pixels[y][x] = r << 16 | g << 8 | b;
}
}
return new Bitmap(pixels);
}
void encode(Bitmap bitmap, File file) throws IOException {
try (BufferedSink sink = Okio.buffer(Okio.sink(file))) {
encode(bitmap, sink);
}
}
/** https://en.wikipedia.org/wiki/BMP_file_format */
void encode(Bitmap bitmap, BufferedSink sink) throws IOException {
int height = bitmap.height();
int width = bitmap.width();
int bytesPerPixel = 3;
int rowByteCountWithoutPadding = (bytesPerPixel * width);
int rowByteCount = ((rowByteCountWithoutPadding + 3) / 4) * 4;
int pixelDataSize = rowByteCount * height;
int bmpHeaderSize = 14;
int dibHeaderSize = 40;
// BMP Header
sink.writeUtf8("BM"); // ID.
sink.writeIntLe(bmpHeaderSize + dibHeaderSize + pixelDataSize); // File size.
sink.writeShortLe(0); // Unused.
sink.writeShortLe(0); // Unused.
sink.writeIntLe(bmpHeaderSize + dibHeaderSize); // Offset of pixel data.
// DIB Header
sink.writeIntLe(dibHeaderSize);
sink.writeIntLe(width);
sink.writeIntLe(height);
sink.writeShortLe(1); // Color plane count.
sink.writeShortLe(bytesPerPixel * Byte.SIZE);
sink.writeIntLe(0); // No compression.
sink.writeIntLe(16); // Size of bitmap data including padding.
sink.writeIntLe(2835); // Horizontal print resolution in pixels/meter. (72 dpi).
sink.writeIntLe(2835); // Vertical print resolution in pixels/meter. (72 dpi).
sink.writeIntLe(0); // Palette color count.
sink.writeIntLe(0); // 0 important colors.
// Pixel data.
for (int y = height - 1; y >= 0; y--) {
for (int x = 0; x < width; x++) {
sink.writeByte(bitmap.blue(x, y));
sink.writeByte(bitmap.green(x, y));
sink.writeByte(bitmap.red(x, y));
}
// Padding for 4-byte alignment.
for (int p = rowByteCountWithoutPadding; p < rowByteCount; p++) {
sink.writeByte(0);
}
}
}
public static void main(String[] args) throws Exception {
BitmapEncoder encoder = new BitmapEncoder();
Bitmap bitmap = encoder.generateGradient();
encoder.encode(bitmap, new File("gradient.bmp"));
}
}
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