Bitmap的优化

这里列出两种常用的Bitmap的优化 ：

public final static Bitmap toRoundCorner(Bitmap bitmap, int pixels) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final RectF rectF = new RectF(rect);
final float roundPx = pixels;
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}

// 通过Options对咱们图片加载进行控制
public static Bitmap sample(byte[] source,int requreHeight,int requreWidth){
// 实例化一个Options
BitmapFactory.Options options = new BitmapFactory.Options();
// 设置为true，decode之后不会生成bitmap，它是对bitmap的基本信息进行获取，信息存在options中
options.inJustDecodeBounds = true;
// 为options进行赋值
BitmapFactory.decodeByteArray(source,0,source.length,options);
// bitmap的高
int outHeight = options.outHeight;
// bitmap的宽
int outWidth = options.outWidth;
// 假如你需要的宽度是400，采样比例应该怎么算
int sampleWidth = outWidth / requreWidth;
//  计算高度采样比率
int sampleHeight = outHeight / requreHeight;
// 获取最大的压缩比率
int sample = Math.max(sampleHeight,sampleWidth);
// 设置压缩比率
options.inSampleSize = sample;
// 不要只读基本信息，边缘了。
options.inJustDecodeBounds = false;

return BitmapFactory.decodeByteArray(source,0,source.length,options());

}