Android应用中实现图片压缩的方法有哪些

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Android图片压缩几种方式总结

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：

质量压缩

采样率压缩

尺寸压缩

Matrix压缩

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 {       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;   }       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;   }       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;   }       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;   }       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;   }       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;   }       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;   }       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();     }   } }