在Android中加载大图片
在Android中加载大图片
提问于 2014-04-10 20:07:33
众所周知，Android在RAM内存中存储位图数据时存在问题。我需要在View上加载一个图像( 13Mpx相机的照片)，然后我需要能够放大和缩小图像。图像应该是可变的。现在它是这样实现的：
BitmapFactory.Options options = new BitmapFactory.Options();
options.inMutable = true;
_bitmap = BitmapFactory.decodeFile(_path, options);当我拍摄一张大照片(13或8mpx)时，程序崩溃并出现“内存不足”错误。我需要一些解决这个问题的方法。我需要一些类，可以加载和操作(缩放它)与大图像。它需要等于或小于API-8。
我尝试了通用图像加载器，但它没有缩放选项。有人知道如何解决这个问题吗？
回答 5
Stack Overflow用户
发布于 2014-04-10 20:13:59
位图占用每个像素4字节==> 13MP等于52MB内存。您应该先使用BitmapFactory.Options来获取大小。通过使用inJustDecodeBounds，您可以获得包含所有元数据的Bitmap对象，但不包含实际图像。
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.id.myimage, options);
int imageHeight = options.outHeight;
int imageWidth = options.outWidth;然后计算屏幕所需的缩放大小：
public static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
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;
// Calculate the largest inSampleSize value that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight
&& (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}并使用它来加载位图的缩放版本：
public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res, resId, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeResource(res, resId, options);
}这一切都在Developer Guide中进行了解释
Stack Overflow用户
发布于 2014-04-10 20:11:16
我推荐使用Square的Picasso库。以及用于图像缩放的PhotoView。
Stack Overflow用户
发布于 2014-04-10 20:13:50
尝试此操作以缩放位图
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
/*
* If set to a value > 1, requests the decoder to
* subsample the original image, returning a smaller
* image to save memory. The sample size is the
* number of pixels in either dimension that
* correspond to a single pixel in the decoded
* bitmap. For example, inSampleSize == 4 returns an
* image that is 1/4 the width/height of the
* original, and 1/16 the number of pixels. Any
* value <= 1 is treated the same as 1. Note: the
* decoder uses a final value based on powers of 2,
* any other value will be rounded down to the
* nearest power of 2.
*/
options.inSampleSize = 2;
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
bitmap = BitmapFactory.decodeFile(path, options);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22987573
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