CameraHelper.java

/*
 * Copyright 2011 Rod Hyde (rod@badlydrawngames.com)
 * 
 * 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.todoroo.zxzx.general;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.math.Vector2;

public final class CameraHelper {

	private CameraHelper () {
	}

	/** Creates an orthographic camera where the "play area" has the given viewport size. The viewport will either be stretched to
	 * fill the entire window, or it will be scaled to maintain the aspect ratio.
	 * 
	 * @param isStretched true if the "play area" is stretched to fill the entire window.
	 * @param virtualWidth the width of the game screen in virtual pixels.
	 * @param virtualHeight the height of the game screen in virtual pixels.
	 * @return the new camera. */
	public static OrthographicCamera createCamera (boolean isStretched, float virtualWidth, float virtualHeight) {
		// Get the viewport size.
		Vector2 viewportSize = viewportSize(isStretched, virtualWidth, virtualHeight);
		float viewportWidth = viewportSize.x;
		float viewportHeight = viewportSize.y;

		// Create the camera, placing the origin at the bottom left of the viewport.
		OrthographicCamera camera = new OrthographicCamera(viewportWidth, viewportHeight);
		float xOrg = (viewportWidth - virtualWidth) / 2;
		float yOrg = (viewportHeight - virtualHeight) / 2;
		camera.position.set(viewportWidth / 2 - xOrg, viewportHeight / 2 - yOrg, 0);
		camera.update();
		return camera;
	}

	/** Calculates the dimensions of the viewport required to support the given virtual coordinates.
	 * 
	 * @param isStretched true if the viewport should be stretched to fill the entire window.
	 * @param virtualWidth the width of the viewport in virtual units.
	 * @param virtualHeight the height of the viewport in virtual units.
	 * @return the viewport's dimensions. */
	public static Vector2 viewportSize (boolean isStretched, float virtualWidth, float virtualHeight) {
		float viewportWidth;
		float viewportHeight;
		if (isStretched) {
			// Stretch the camera to fill the entire screen.
			viewportWidth = virtualWidth;
			viewportHeight = virtualHeight;
		} else {
			// Maintain the aspect ratio by letterboxing.
			float aspect = virtualWidth / virtualHeight;
			float physicalWidth = Gdx.graphics.getWidth();
			float physicalHeight = Gdx.graphics.getHeight();
			if (physicalWidth / physicalHeight >= aspect) {
				// Letterbox left and right.
				viewportHeight = virtualHeight;
				viewportWidth = viewportHeight * physicalWidth / physicalHeight;
			} else {
				// Letterbox above and below.
				viewportWidth = virtualWidth;
				viewportHeight = viewportWidth * physicalHeight / physicalWidth;
			}
		}
		return new Vector2(viewportWidth, viewportHeight);
	}

	public static enum ViewportMode {
		PIXEL_PERFECT, STRETCH_TO_ASPECT, STRETCH_TO_SCREEN
	}

	public static OrthographicCamera createCamera2 (ViewportMode viewportMode, float virtualWidth, float virtualHeight,
		float density) {
		// Get the viewport size.
		Vector2 viewportSize = sizeToDensity(viewportMode, virtualWidth, virtualHeight, density);
		float viewportWidth = viewportSize.x;
		float viewportHeight = viewportSize.y;

		// Create the camera, placing the origin at the bottom left of the viewport.
		OrthographicCamera camera = new OrthographicCamera(viewportWidth, viewportHeight);
		float xOrg = (viewportWidth - virtualWidth) / 2;
		float yOrg = (viewportHeight - virtualHeight) / 2;
		camera.position.set(viewportWidth / 2 - xOrg, viewportHeight / 2 - yOrg, 0);
		camera.update();
		return camera;
	}

	public static Vector2 sizeToDensity (ViewportMode viewportMode, float virtualWidth, float virtualHeight, float density) {
		float viewportWidth = virtualWidth;
		float viewportHeight = virtualHeight;
		float physicalWidth = Gdx.graphics.getWidth();
		float physicalHeight = Gdx.graphics.getHeight();
		if (viewportMode == ViewportMode.PIXEL_PERFECT) {
			float widthAtDensity = viewportWidth * density;
			float heightAtDensity = viewportHeight * density;
			viewportWidth *= (physicalWidth / widthAtDensity);
			viewportHeight *= (physicalHeight / heightAtDensity);
		} else if (viewportMode == ViewportMode.STRETCH_TO_ASPECT) {
			float aspect = virtualWidth / virtualHeight;
			if (physicalWidth / physicalHeight >= aspect) {
				// Letterbox left and right.
				viewportHeight = virtualHeight;
				viewportWidth = viewportHeight * physicalWidth / physicalHeight;
			} else {
				// Letterbox above and below.
				viewportWidth = virtualWidth;
				viewportHeight = viewportWidth * physicalHeight / physicalWidth;
			}
		}
		return new Vector2(viewportWidth, viewportHeight);
	}

	public static float bestDensity (float virtualWidth, float virtualHeight, float[] densities) {
		// TODO: Spell out that densities is assumed to be in ascending order.
		float bestDensity = densities[0];
		float physicalWidth = Gdx.graphics.getWidth();
		float physicalHeight = Gdx.graphics.getHeight();
		for (int i = 1; i < densities.length; i++) {
			float density = densities[i];
			float widthAtDensity = density * virtualWidth;
			float heightAtDensity = density * virtualHeight;
			if (widthAtDensity > physicalWidth || heightAtDensity > physicalHeight) {
				break;
			}
			bestDensity = density;
		}
		return bestDensity;
	}
}