我有问题BitmapFactory.decodeStream(inputStream)
。当不带选项使用它时,它将返回一个图像。但是当我将它与选项一起使用时,如.decodeStream(inputStream, null, options)
它永远不会返回位图。
我想做的是在实际加载位图之前对其进行下采样以节省内存。
我读过一些很好的指南,但没有使用.decodeStream
.
处理大位图
And here
Android 中的图像处理
效果很好
URL url = new URL(sUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);
不起作用
InputStream is = connection.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is, null, options);
InputStream is = connection.getInputStream();
Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(is, null, options);
Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);
if (options.outHeight * options.outWidth * 2 >= 200*100*2){
// Load, scaling to smallest power of 2 that'll get it <= desired dimensions
double sampleSize = scaleByHeight
? options.outHeight / TARGET_HEIGHT
: options.outWidth / TARGET_WIDTH;
options.inSampleSize =
(int)Math.pow(2d, Math.floor(
Math.log(sampleSize)/Math.log(2d)));
}
// Do the actual decoding
options.inJustDecodeBounds = false;
Bitmap img = BitmapFactory.decodeStream(is, null, options);
问题是,一旦您使用 HttpUrlConnection 中的 InputStream 来获取图像元数据,您就无法倒回并再次使用相同的 InputStream。
因此,您必须创建一个新的输入流来进行图像的实际采样。
Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(is, null, options);
Boolean scaleByHeight = Math.abs(options.outHeight - TARGET_HEIGHT) >= Math.abs(options.outWidth - TARGET_WIDTH);
if(options.outHeight * options.outWidth * 2 >= 200*200*2){
// Load, scaling to smallest power of 2 that'll get it <= desired dimensions
double sampleSize = scaleByHeight
? options.outHeight / TARGET_HEIGHT
: options.outWidth / TARGET_WIDTH;
options.inSampleSize =
(int)Math.pow(2d, Math.floor(
Math.log(sampleSize)/Math.log(2d)));
}
// Do the actual decoding
options.inJustDecodeBounds = false;
is.close();
is = getHTTPConnectionInputStream(sUrl);
Bitmap img = BitmapFactory.decodeStream(is, null, options);
is.close();
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