获取Bitmap大小

/** 
  * 得到bitmap的大小 
  */  
 public static int getBitmapSize(Bitmap bitmap) {  
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {    //API 19  
         return bitmap.getAllocationByteCount();  
     }  
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR1) {//API 12  
         return bitmap.getByteCount();  
     }  
     // 在低版本中用一行的字节x高度  
     return bitmap.getRowBytes() * bitmap.getHeight();                //earlier version  
 }  

Bitmap优化

一、主动释放Bitmap资源

if(bitmap != null && !bitmap.isRecycled()){  
    bitmap.recycle(); 
    bitmap = null; 
}

二、主动释放ImageView的图片资源

private static void recycleImageViewBitMap(ImageView imageView) {
        if (imageView != null) {
            BitmapDrawable bd = (BitmapDrawable) imageView.getDrawable();
            rceycleBitmapDrawable(bd);
        }
}

private static void rceycleBitmapDrawable(BitmapDrawable bitmapDrawable) {
        if (bitmapDrawable != null) {
            Bitmap bitmap = bitmapDrawable.getBitmap();
            rceycleBitmap(bitmap);
        }
        bitmapDrawable = null;
}

private static void rceycleBitmap(Bitmap bitmap) {
        if (bitmap != null && !bitmap.isRecycled()) {
            bitmap.recycle();
            bitmap = null;
        }
}

三、主动释放ImageView的背景资源

public static void recycleBackgroundBitMap(ImageView view) {
        if (view != null) {
            BitmapDrawable bd = (BitmapDrawable) view.getBackground();
            rceycleBitmapDrawable(bd);
        }
}
private static void rceycleBitmapDrawable(BitmapDrawable bitmapDrawable) {
        if (bitmapDrawable != null) {
            Bitmap bitmap = bitmapDrawable.getBitmap();
            rceycleBitmap(bitmap);
        }
        bitmapDrawable = null;
}
private static void rceycleBitmap(Bitmap bitmap) {
        if (bitmap != null && !bitmap.isRecycled()) {
            bitmap.recycle();
            bitmap = null;
        }
}

四、尽量少用Png图，多用NinePatch,WebP的图

五、使用大图之前，尽量先对其进行压缩

1.质量压缩

ByteArrayOutputStream baos = newByteArrayOutputStream();

intquality = Integer.valueOf(editText.getText().toString());

bit.compress(CompressFormat.JPEG, quality, baos);

byte[] bytes = baos.toByteArray();

bm = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

Log.i("wechat", "压缩后图片的大小"+ (bm.getByteCount() / 1024/ 1024)

    + "M宽度为"+ bm.getWidth() + "高度为"+ bm.getHeight()

    + "bytes.length= "+ (bytes.length / 1024) + "KB"

    + "quality="+ quality);

其中quality是从edittext获取的数字，可以从0–100改变，这里出来的log是：

image.png

2.采样率压缩

BitmapFactory.Options options = newBitmapFactory.Options();
options.inSampleSize = 2;
bm = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath()
         + "/DCIM/Camera/test.jpg", options);
Log.i("wechat", "压缩后图片的大小"+ (bm.getByteCount() / 1024/ 1024)+ "M宽度为"+ bm.getWidth() + "高度为"+ bm.getHeight());

出来的log是

image.png

3.缩放法压缩（martix）

Matrix matrix = newMatrix();
matrix.setScale(0.5f, 0.5f);
bm = Bitmap.createBitmap(bit, 0, 0, bit.getWidth(),bit.getHeight(), matrix, true);
Log.i("wechat", "压缩后图片的大小"+ (bm.getByteCount() / 1024/ 1024)
+ "M宽度为"+ bm.getWidth() + "高度为"+ bm.getHeight());

出来的log是

image.png

4.RGB_565法

BitmapFactory.Options options2 = newBitmapFactory.Options();
options2.inPreferredConfig = Bitmap.Config.RGB_565;
bm = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath()
         + "/DCIM/Camera/test.jpg", options2);
Log.i("wechat", "压缩后图片的大小"+ (bm.getByteCount() / 1024/ 1024)+ "M宽度为"+ bm.getWidth() + "高度为"+ bm.getHeight());

出来的log是：

image.png

5.createScaledBitmap

bm = Bitmap.createScaledBitmap(bit, 150, 150, true);
Log.i("wechat", "压缩后图片的大小"+ (bm.getByteCount() / 1024) + "KB宽度为"+ bm.getWidth() + "高度为"+ bm.getHeight());

出来的log是

image.png

六、LruCache，DiskLruCache