BitmapUtil.java

package at.favre.lib.dali.util;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.util.Log;

import java.io.File;
import java.io.FileOutputStream;

/**
 * Created by PatrickF on 26.05.2014.
 */
public class BitmapUtil {
	private static final String TAG = BitmapUtil.class.getSimpleName();

	private BitmapUtil() {}

	public static void clearCacheDir(File cacheDir) {
		File[] files = cacheDir.listFiles();

		if (files != null) {
			for (File file : files)
				file.delete();
		}
	}

	public static Bitmap loadBitmapFromResId(int resId, Resources resources) {
		return BitmapFactory.decodeResource(resources, resId);
	}


	public static File saveBitmapDownscaled(Bitmap bitmap, String filename, String path, boolean recycle, int maxWidth, int maxHeight) {
		float heightScaleFactor = 1;
		float widthScaleFactor = 1;
		float scaleFactor = 1;

		if(bitmap.getHeight() > maxHeight) {
			heightScaleFactor = (float) maxHeight / (float) bitmap.getHeight();
		}

		if(bitmap.getWidth() > maxWidth) {
			widthScaleFactor = (float) maxWidth / (float) bitmap.getWidth();
		}
		if(heightScaleFactor < 1 || widthScaleFactor < 1) {
			scaleFactor = Math.min(heightScaleFactor,widthScaleFactor);
		}
		bitmap = Bitmap.createScaledBitmap(bitmap,(int) (bitmap.getWidth()*scaleFactor),(int) (bitmap.getHeight()*scaleFactor) ,true);
		return saveBitmap(bitmap,filename,path,recycle);
	}

	public static File saveBitmap(Bitmap bitmap, String filename, String path, boolean recycle) {
		FileOutputStream out=null;
		try {
			File f = new File(path,filename);
			if(!f.exists()) {
				f.createNewFile();
			}
			out = new FileOutputStream(f);
			if(bitmap.compress(Bitmap.CompressFormat.PNG, 90, out)) {
				return f;
			}
		} catch (Exception e) {
			Log.e(TAG, "Could not save bitmap", e);
		} finally {
			try{
				out.close();
			} catch(Throwable ignore) {}
			if(recycle) {
				bitmap.recycle();
			}
		}
		return null;
	}

	/**
	 * Mirrors the given bitmap
	 */

	public static Bitmap flip(Bitmap src) {
		Matrix m = new Matrix();
		m.preScale(-1, 1);
		return Bitmap.createBitmap(src, 0, 0, src.getWidth(), src.getHeight(), m, false);
	}


	/**
	 *
	 * @param bmp input bitmap
	 * @param contrast 0..10 1 is default
	 * @param brightness -255..255 0 is default
	 * @return new bitmap
	 */
	public static Bitmap changeBitmapContrastBrightness(Bitmap bmp, float contrast, float brightness)
	{
		ColorMatrix cm = new ColorMatrix(new float[]
				{
						contrast, 0, 0, 0, brightness,
						0, contrast, 0, 0, brightness,
						0, 0, contrast, 0, brightness,
						0, 0, 0, 1, 0
				});

		Bitmap ret = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());

		Canvas canvas = new Canvas(ret);

		Paint paint = new Paint();
		paint.setColorFilter(new ColorMatrixColorFilter(cm));
		canvas.drawBitmap(bmp, 0, 0, paint);

		return ret;
	}


	public static int getInSampleSizeFromScale(float scale, boolean keepPowOfTwo) {
		int insample = 1;
		float scaleThreshold = 1.f;

		while(scaleThreshold >= scale) {
			if(keepPowOfTwo) {
				insample *= 2;
			} else {
				insample += 1;
			}

			scaleThreshold = scaleThreshold / insample;
		}

		if(keepPowOfTwo) {
			return insample / 2;
		} else {
			return insample - 1;
		}
	}
}