Android使用BitmapFactory.Options解决加载大图片内存溢出问题-优快云博客

本文介绍如何在Android应用中通过调整Bitmap加载参数来优化大图片内存使用，避免内存溢出，包括设置缩放大小、计算图片缩放比例及图片转Base64字符串过程。

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由于Android对图片使用内存有限制，若是加载几兆的大图片便内存溢出。Bitmap会将图片的所有像素（即长x宽）加载到内存中，如果图片分辨率过大，会直接导致内存溢出（java.lang.OutOfMemoryError），只有在BitmapFactory加载图片时使用BitmapFactory.Options对相关参数进行配置来减少加载的像素。

1、设置缩放大小对图片作处理

public Bitmap getBitmapFromFile(File dst, int width, int height) {
if (null != dst && dst.exists()) {
BitmapFactory.Options opts = null;
if (width > 0 && height > 0) {
opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(dst.getPath(), opts);
// 计算图片缩放比例
final int minSideLength = Math.min(width, height);
opts.inSampleSize = computeSampleSize(opts, minSideLength,
width * height);
opts.inJustDecodeBounds = false;
opts.inInputShareable = true;
opts.inPurgeable = true;
}
try {
return BitmapFactory.decodeFile(dst.getPath(), opts);
} catch (OutOfMemoryError e) {
e.printStackTrace();
}
}
return null;
}

public static int computeSampleSize(BitmapFactory.Options options,
int minSideLength, int maxNumOfPixels) {
int initialSize = computeInitialSampleSize(options, minSideLength,
maxNumOfPixels);

int roundedSize;
if (initialSize <= 8) {
roundedSize = 1;
while (roundedSize < initialSize) {
roundedSize <<= 1;
}
} else {
roundedSize = (initialSize + 7) / 8 * 8;
}

return roundedSize;
}

private static int computeInitialSampleSize(BitmapFactory.Options options,
int minSideLength, int maxNumOfPixels) {
double w = options.outWidth;
double h = options.outHeight;

int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math
.sqrt(w * h / maxNumOfPixels));
int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(Math
.floor(w / minSideLength), Math.floor(h / minSideLength));

if (upperBound < lowerBound) {
// return the larger one when there is no overlapping zone.
return lowerBound;
}

if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
return 1;
} else if (minSideLength == -1) {
return lowerBound;
} else {
return upperBound;
}
}

/**
* 图片转换成字符串[BASE64]
*
* @return
*/
public String getImageBinary(String path) {
System.out.println("path--->" + path);
try {

Bitmap bitmap = getBitmapFromFile(new File(path),640,640);//scalePicture(path,640,640);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(CompressFormat.PNG,100,baos);
String uploadBuffer = new String(Base64.encodeToString(baos.toByteArray(),Base64.DEFAULT));
baos.flush();
baos.close();
System.out.println("图片信息转换成字符串为：---->" + uploadBuffer);
return uploadBuffer;
}
catch(IOException e)
{
e.printStackTrace();
}
catch (Exception e) {
e.printStackTrace();
}

return null;
}