AndroidImageUtil.java

public final class AndroidImageUtil {

    private AndroidImageUtil() {
    }

    /**
     * 按图片尺寸压缩时，无法准确知道压缩后的文件大小。
     * http://stackoverflow.com/questions/477572/strange-out-of-memory-issue-while-loading-an-image-to-a-bitmap-object/823966#823966
     * @param file
     * @return
     */
    public static void compressImageByImageSize(File file, int newImageSize) {
        //Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;

        try {
            FileInputStream fis = new FileInputStream(file);
            BitmapFactory.decodeStream(fis, null, o);
            fis.close();

            int scale = 1;
            if (o.outHeight > newImageSize || o.outWidth > newImageSize) {
                scale = (int) Math.pow(
                    2,
                    (int) Math.ceil(
                        Math.log(newImageSize / (double) Math.max(o.outHeight, o.outWidth))
                            / Math.log(0.5)
                    )
                );
            }

            //Decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            fis = new FileInputStream(file);
            Bitmap b = BitmapFactory.decodeStream(fis, null, o2);
            fis.close();

            file.createNewFile();
            FileOutputStream outputStream = new FileOutputStream(file);

            b.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);

        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * http://www.graphicsmill.com/blog/2014/11/06/Compression-ratio-for-different-JPEG-quality-values#.V_5HeY997_U
     * todo 初始文件6.xM，decode后82M（大文件恐怕会内存溢出），100压缩12M,95压缩6M...
     * 曲线怪异。不如按图片尺寸压缩来的方便
     * @param file
     * @param fileSize
     * @deprecated
     */
    public static void compressImageByFileSize(File file, int fileSize) {

        long length = file.length();
        if (length <= fileSize) return;

        Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());

        int quality = 100 - bitmap.getByteCount() * 6 / fileSize;//105;
        ByteArrayOutputStream output = new ByteArrayOutputStream();

        try {

            byte[] bytes = null;
            while (length >= fileSize && quality > 5) {
                output.flush();  //to avoid out of memory error
                output.reset();
                quality -= 5;
                bitmap.compress(Bitmap.CompressFormat.JPEG, quality, output);
                bytes = output.toByteArray();
                length = bytes.length;
                Log.d(Util.class.getName(), "length=" + length + ";quality=" + quality);
            }

            FileOutputStream fo = new FileOutputStream(file);
            fo.write(bytes);
            fo.flush();
            fo.close();

        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}