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/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * 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 com.badlogic.gdx.utils;

import java.nio.ByteBuffer;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.graphics.Pixmap;
import com.badlogic.gdx.graphics.Pixmap.Format;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import com.badlogic.gdx.math.MathUtils;

/** Class with static helper methods that provide access to the default OpenGL FrameBuffer. These methods can be used to get the
 * entire screen content or a portion thereof.
 * 
 * @author espitz */
public class ScreenUtils {

	/** Returns the default framebuffer contents as a {@link TextureRegion} with a width and height equal to the current screen
	 * size. The base {@link Texture} always has {@link MathUtils#nextPowerOfTwo} dimensions and RGBA8888 {@link Format}. It can be
	 * accessed via {@link TextureRegion#getTexture}. The texture is not managed and has to be reloaded manually on a context loss.
	 * The returned TextureRegion is flipped along the Y axis by default. */
	public static TextureRegion getFrameBufferTexture () {
		final int w = Gdx.graphics.getWidth();
		final int h = Gdx.graphics.getHeight();
		return getFrameBufferTexture(0, 0, w, h);
	}

	/** Returns a portion of the default framebuffer contents specified by x, y, width and height as a {@link TextureRegion} with
	 * the same dimensions. The base {@link Texture} always has {@link MathUtils#nextPowerOfTwo} dimensions and RGBA8888
	 * {@link Format}. It can be accessed via {@link TextureRegion#getTexture}. This texture is not managed and has to be reloaded
	 * manually on a context loss. If the width and height specified are larger than the framebuffer dimensions, the Texture will
	 * be padded accordingly. Pixels that fall outside of the current screen will have RGBA values of 0.
	 * 
	 * @param x the x position of the framebuffer contents to capture
	 * @param y the y position of the framebuffer contents to capture
	 * @param w the width of the framebuffer contents to capture
	 * @param h the height of the framebuffer contents to capture */
	public static TextureRegion getFrameBufferTexture (int x, int y, int w, int h) {
		Gdx.gl.glPixelStorei(GL10.GL_PACK_ALIGNMENT, 1);
		final int potW = MathUtils.nextPowerOfTwo(w);
		final int potH = MathUtils.nextPowerOfTwo(h);

		final Pixmap pixmap = new Pixmap(potW, potH, Format.RGBA8888);
		ByteBuffer pixels = pixmap.getPixels();
		Gdx.gl.glReadPixels(x, y, potW, potH, GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, pixels);

		Texture texture = new Texture(pixmap);
		TextureRegion textureRegion = new TextureRegion(texture, 0, h, w, -h);
		pixmap.dispose();

		return textureRegion;
	}

	/** Returns the default framebuffer contents as a byte[] array with a length equal to screen width * height * 4. The byte[] will
	 * always contain RGBA8888 data. Because of differences in screen and image origins the framebuffer contents should be flipped
	 * along the Y axis if you intend save them to disk as a bitmap. Flipping is not a cheap operation, so use this functionality
	 * wisely.
	 * 
	 * @param flipY whether to flip pixels along Y axis */
	public static byte[] getFrameBufferPixels (boolean flipY) {
		final int w = Gdx.graphics.getWidth();
		final int h = Gdx.graphics.getHeight();
		return getFrameBufferPixels(0, 0, w, h, flipY);
	}

	/** Returns a portion of the default framebuffer contents specified by x, y, width and height, as a byte[] array with a length
	 * equal to the specified width * height * 4. The byte[] will always contain RGBA8888 data. If the width and height specified
	 * are larger than the framebuffer dimensions, the Texture will be padded accordingly. Pixels that fall outside of the current
	 * screen will have RGBA values of 0. Because of differences in screen and image origins the framebuffer contents should be
	 * flipped along the Y axis if you intend save them to disk as a bitmap. Flipping is not cheap operation, so use this
	 * functionality wisely.
	 * 
	 * @param flipY whether to flip pixels along Y axis */
	public static byte[] getFrameBufferPixels (int x, int y, int w, int h, boolean flipY) {
		Gdx.gl.glPixelStorei(GL10.GL_PACK_ALIGNMENT, 1);
		final ByteBuffer pixels = BufferUtils.newByteBuffer(w * h * 4);
		Gdx.gl.glReadPixels(x, y, w, h, GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, pixels);
		final int numBytes = w * h * 4;
		byte[] lines = new byte[numBytes];
		if (flipY) {
			final int numBytesPerLine = w * 4;
			for (int i = 0; i < h; i++) {
				pixels.position((h - i - 1) * numBytesPerLine);
				pixels.get(lines, i * numBytesPerLine, numBytesPerLine);
			}
		} else {
			pixels.clear();
			pixels.get(lines);
		}
		return lines;

	}
}