Bitmap在Android中指的是一张图片。通过BitmapFactory类提供的四类方法：decodeFile,decodeResource,decodeStream和decodeByteArray,分别从文件系统，资源，输入流和字节数组中加载出一个Bitmap对象。
本文以decodeResource方式说明。
public BitmapdecodeBitmap(int width, int height) {
BitmapFactory.Options op =new BitmapFactory.Options();
op.inJustDecodeBounds =true;//获取bitmap的原始宽高信息，不生成bitmap
Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), R.mipmap.test, op);
int originalWidth = op.outWidth;
int originalHeight = op.outHeight;
op.inJustDecodeBounds =false;//根据采样率真正生成压缩后的bitmap
op.inSampleSize = getSampleSize(originalWidth, originalHeight, width, height);
Bitmap bitmap1 = BitmapFactory.decodeResource(context.getResources(), R.mipmap.test, op);
Log.d("bitmapUtil", "bitmap: " + bitmap1.getByteCount());
return bitmap1;
}
private int getSampleSize(int originalWidth, int originalHeight, int width, int height) {
// 初始化采样率
int sampleSize =1;
if (originalWidth > originalHeight && originalWidth > width) {
Log.d("bitmapUtil", "originalwidth: " + originalWidth);
Log.d("bitmapUtil", "width: " + width);
// 用宽度计算采样率
sampleSize = originalWidth / width;
}else if (originalWidth < originalHeight && originalHeight > height) {
Log.d("bitmapUtil", "originalHeight: " + originalHeight);
Log.d("bitmapUtil", "height: " + height);
// 用高度计算采样率
sampleSize = originalHeight / height;
}
if (sampleSize <=0) {
sampleSize =1;
}
return sampleSize;
}
