德code字节数组位图，它已经融为一体pressed在Java中 [英] Decode byte array to bitmap that has been compressed in Java

问题描述

我玉米$ P $以下列方式pssing位图<​​/ P>

I am compressing a bitmap in the following way

Bitmap bmpSig = getMyBitMap();
int size = bmpSig.getWidth() * bmpSig.getHeight();
ByteArrayOutputStream out = new ByteArrayOutputStream(size);
bmpSig.compress(Bitmap.CompressFormat.JPEG, 100, out);   
byte[] bytSig = out.toByteArray();

我则试图从字节数组中的Andr​​oid ImageView的显示图像。当我这样做，我得到的图像是全黑的图像。

I am then trying to display the image in an Android ImageView from the byte array. When I do this I get an image that is completely black image.

ImageView myImg = (ImageView) findViewById(R.id.img_view);
myImg.setImageBitmap(BitmapFactory.decodeByteArray(bytSig, 0, bytSig.length));

我猜想这是因为我很想念BitmapFactory.de codeByteArray（）之前的一个步骤扭转JPEG COM pression。还是我误解了如何COM pression工作？

I'm assuming it's because I am missing a step before BitmapFactory.decodeByteArray() to reverse the jpeg compression. Or have I misunderstood how the compression works?

推荐答案

我不知道，我的位图的背景（从Canvas对象）是透明的。由于该位图是在白色背景上仅仅黑色线的黑色图象是由于玉米pressing至JPEG它所产生的图像在黑色背景

I didn't realise that the background of my bitmap (from a Canvas object) was transparent. Since this bitmap is just black lines on a white background the black image is due to compressing to JPEG giving the image a black background.

我已经改变了

bmpSig.compress(Bitmap.CompressFormat.JPEG, 100, out); 

到

bmpSig.compress(Bitmap.CompressFormat.PNG, 100, out); 

和它工作正常。

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