Android图片压缩几种方式

我会带着你远行 2022-09-28 01:21 455阅读 0赞

图片压缩在Android开发中很常见也很重要，防止图片的OOM也是压缩的重要原因。

首先看下Bitmap图片文件的大小的决定因素：

Bitmap所占用的内存 = 图片长度 x 图片宽度 x 一个像素点占用的字节数。3个参数，任意减少一个的值，就达到了压缩的效果。

接下来看下Bitmap图片的几种格式的特点：  
ALPHA\_8  
 表示8位Alpha位图,即A=8,一个像素点占用1个字节,它没有颜色,只有透明度  
 ARGB\_4444  
表示16位ARGB位图，即A=4,R=4,G=4,B=4,一个像素点占4+4+4+4=16位，2个字节  
ARGB\_8888  
表示32位ARGB位图，即A=8,R=8,G=8,B=8,一个像素点占8+8+8+8=32位，4个字节  
RGB\_565  
表示16位RGB位图,即R=5,G=6,B=5,它没有透明度,一个像素点占5+6+5=16位，2个字节

如果进行图片格式的压缩的话，一般情况下都是ARGB\_8888转为RGB565进行压缩。

写了一个工具类，基本上列举了Android上图片的几种基本压缩方式：

1.质量压缩

2.采样率压缩

3.尺寸压缩

4.Matrix压缩

5.图片格式的压缩，例如PNG和JPG保存后的图片大小是不同的

public class Utils {
    
        /**
         * 采样率压缩
         *
         * @param bitmap
         * @param sampleSize 采样率为2的整数倍，非整数倍四舍五入，如4的话，就是原图的1/4
         * @return 尺寸变化
         */
        public static Bitmap getBitmap(Bitmap bitmap, int sampleSize) {
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inSampleSize = sampleSize;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
            byte[] bytes = baos.toByteArray();
            Bitmap bit = BitmapFactory.decodeByteArray(bytes, 0, bytes.length, options);
            Log.i("info", "图片大小：" + bit.getByteCount());//2665296   10661184
            return bit;
        }
    
        /**
         * 图片质量压缩
         *
         * @param bitmap
         * @param quality
         * @return 尺寸不变，质量变小
         */
        public static Bitmap compressByQuality(Bitmap bitmap, int quality) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, quality, baos);
            byte[] bytes = baos.toByteArray();
            Bitmap bit = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            Log.i("info", "图片大小：" + bit.getByteCount());//10661184
            return bit;
        }
    
        /**
         * 图片质量压缩
         *
         * @param src
         * @param maxByteSize
         * @return
         */
        public static Bitmap compressByQuality(Bitmap src, long maxByteSize) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            int quality = 100;
            src.compress(Bitmap.CompressFormat.JPEG, quality, baos);
            while (baos.toByteArray().length > maxByteSize && quality > 0) {
                baos.reset();
                src.compress(Bitmap.CompressFormat.JPEG, quality -= 5, baos);
            }
            if (quality < 0) return null;
            byte[] bytes = baos.toByteArray();
            Bitmap bit = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            return bit;
        }
    
        public static Bitmap compressByFormat(Bitmap bitmap, int format) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
            byte[] bytes = baos.toByteArray();
            Bitmap bit = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            Log.i("info", "图片大小：" + bit.getByteCount());//10661184
            return bit;
        }
    
        /**
         * Matrix缩放
         *
         * @param bitmap
         * @param scaleWidth
         * @param scaleHeight
         * @return 尺寸和大小变化
         */
        public static Bitmap getBitmapBySize(Bitmap bitmap, float scaleWidth, float scaleHeight) {
            Matrix matrix = new Matrix();
            matrix.postScale(scaleWidth, scaleHeight);
            Bitmap bit = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
            Log.i("info", "图片大小：" + bit.getByteCount());
            return bit;
        }
    
        /**
         * 按照图片格式配置压缩
         *
         * @param path
         * @param config ALPHA_8,ARGB_4444,ARGB_8888,RGB_565;
         * @return RGB_565比ARGB_8888节省一半内存
         */
        public static Bitmap getBitmapByFormatConfig(String path, Bitmap.Config config) {
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inPreferredConfig = config;
            Bitmap bitmap = BitmapFactory.decodeFile(path, options);
            Log.i("info", "图片大小：" + bitmap.getByteCount());
            return bitmap;
        }
    
        /**
         * 指定大小缩放
         *
         * @param bitmap
         * @param width
         * @param height
         * @return
         */
        public static Bitmap getBitmapByScaleSize(Bitmap bitmap, int width, int height) {
            Bitmap bit = Bitmap.createScaledBitmap(bitmap, width, height, true);
            Log.i("info", "图片大小：" + bit.getByteCount());
            return bit;
        }
    
        /**
         * 通过保存格式压缩
         *
         * @param bitmap
         * @param format JPEG,PNG,WEBP
         * @return
         */
        public static Bitmap getBitmapByFormat(Bitmap bitmap, Bitmap.CompressFormat format) {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            bitmap.compress(format, 100, baos);
            byte[] bytes = baos.toByteArray();
            Bitmap bit = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
            Log.i("info", "图片大小：" + bit.getByteCount());
            return bit;
        }
    
        /**
         * 文件加载压缩
         *
         * @param filePath
         * @param inSampleSize
         * @return
         */
        public static Bitmap getBitmap(String filePath, int inSampleSize) {
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            BitmapFactory.decodeFile(filePath, options);//此时不耗费和占用内存
            options.inSampleSize = inSampleSize;
            options.inJustDecodeBounds = false;
            return BitmapFactory.decodeFile(filePath, options);
        }
    
        public static Bitmap getBitmap(String filePath) {
            return BitmapFactory.decodeFile(filePath);
        }
    
        public static Bitmap view2Bitmap(View view) {
            if (view == null) return null;
            Bitmap ret = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(ret);
            Drawable bgDrawable = view.getBackground();
            if (bgDrawable != null) {
                bgDrawable.draw(canvas);
            } else {
                canvas.drawColor(Color.WHITE);
            }
            view.draw(canvas);
            return ret;
        }
    
        public static void saveBitmap(Bitmap bitmap) {
            File file = new File(Environment.getExternalStorageDirectory() + "/img.jpg");
            try {
                FileOutputStream fileOutputStream = new FileOutputStream(file);
                bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fileOutputStream);
                fileOutputStream.flush();
                fileOutputStream.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        public static void saveBitmap(Bitmap bitmap,Bitmap.CompressFormat format) {
            File file = new File(Environment.getExternalStorageDirectory() + "/img.jpg");
            try {
                FileOutputStream fileOutputStream = new FileOutputStream(file);
                bitmap.compress(format, 100, fileOutputStream);
                fileOutputStream.flush();
                fileOutputStream.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }