BitmapFactory.decodeByteArray() 返回 NULL

2022-01-08 00:00:00 format image camera android java

我正在使用相机的 previewCallback 来尝试抓取图像.这是我正在使用的代码

I am using the previewCallback from the camera to try and grab images. Here is the code I am using

private Camera.PreviewCallback mPrevCallback = new Camera.PreviewCallback() 
{
        public void onPreviewFrame( byte[] data, Camera Cam ) {
                Log.d("CombineTestActivity", "Preview started");
                Log.d("CombineTestActivity", "Data length = " 
                        + data.length );
                currentprev = BitmapFactory.decodeByteArray( data, 0, 
                        data.length );

               if( currentprev == null )
                   Log.d("CombineTestActivity", "currentprev is null" );

                Log.d("CombineTestActivity", "Preview Finished" );

        }
};

数据的长度总是与576000相同.

the length of the data always comes otu the same as 576000.

我还尝试更改相机的参数，以便图像以不同的格式返回.这是我这样做时的样子.

Also I have tried changing the parameters of the camera so the image comes back as different formats. Here is what it looks like when I do that.

mCamera = Camera.open();
camParam = mCamera.getParameters();
camParam.setPreviewFormat( ImageFormat.RGB_565 );
mCamera.setParameters( camParam );
    mCamera.setPreviewCallback( mPrevCallback );

但是，当我更改预览格式以及将其保留为 NV21 的默认值时，BitmapFactory.decodeByteArray 返回为空.我还尝试将预览格式更改为 JPEG 类型.我什至在 ddms 中得到了一个调试语句，这就是我得到的

However both when I change the preview format and when I leave it as its default of NV21, BitmapFactory.decodeByteArray comes back as null. I have also tried changing the preview format to JPEG type. I even get a debug statement in the ddms, this is what I get

D/skia (14391): --- SkImageDecoder::Factory 返回 null"

"D/skia (14391): --- SkImageDecoder::Factory returned null"

推荐答案

好的，希望这会有所帮助.

Alright, hopefully this will help.

搜索互联网寻找快速解决方案，并找到了完美的东西.

Scoured the internet looking for a fast solution, and found the perfect thing.

这适用于 Android 2.1

感谢 此页面的 off3nsiv3.

Thanks to off3nsiv3 from this page.

// Convert to JPG
Size previewSize = camera.getParameters().getPreviewSize(); 
YuvImage yuvimage=new YuvImage(data, ImageFormat.NV21, previewSize.width, previewSize.height, null);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
yuvimage.compressToJpeg(new Rect(0, 0, previewSize.width, previewSize.height), 80, baos);
byte[] jdata = baos.toByteArray();

// Convert to Bitmap
Bitmap bmp = BitmapFactory.decodeByteArray(jdata, 0, jdata.length);

只需对 off3nsiv3 的代码稍作修改即可.与手动解码相比，FPS 仍然非常高.

Just a little modification to off3nsiv3's code and you're set. The FPS is still incredibly high compared to manual decoding.

对于上面的代码，80 是 jpeg 质量(0 从 100，100 最好).

For the above code, the 80 is the jpeg quality (0 from 100, 100 being best).

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