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BitmapFactory类提供了四类方法:decodeFile, decodeResource, decodeStream和decodeByteArray
分别用于支持从文件系统,资源,输入流以及字节数组中加载出一个Bitmap对象,前两者又间接调用了decodeStream
为了避免OOM,可以通过采样率有效的加载图片
如果获取采样率?
1.将BitmapFactory.Options的inJustDecodeBounds的参数设置为true并加载图片
2.从BitmapFactory.Options中取出图片的原始宽高,它们对应outWidth和outHeight参数
3.根据采样率的规则并结合目标View的所需大小计算采样率inSampleSize
4.将BitmapFactory.Options的inJustDecodeBounds的参数设置为false,并重新加载图片
上述步骤通过代码体现:
public static Bitmap decodeSampledBitmapFromResource(Resource res, int resId, int reqWidth, int reqHeight){ final BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeResource(res, resId, options); options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); options.inJustDecodeBounds = false; return BitmapFactory.decodeResource(res, resId, options); } public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight){ final int height = options.outHeight; final int width = options.outWidth; int inSampleSize = 1; if(height > reqHeight || width > reqWidth){ final int halfHeight = height / 2; final int halfWidth = width / 2; while((halfHeight / inSampleSize) >= reqHeight && (halfWidth / inSampleSize) >= reqWidth){ inSampleSize *= 2; } } return inSampleSize; }
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原文地址：http://www.cnblogs.com/cxsy/p/5771270.html
