java - 在 Android 中从位图保存图像时如何设置 dpi 图像？

Question

我使用这个函数将位图保存到 sdcard 上的文件中:

private static File storeImage(Context context, Bitmap image) {
    File pictureFile = getOutputMediaFile(context);
    if (pictureFile == null) {
        return null;
    }
    try {
        FileOutputStream fos = new FileOutputStream(pictureFile);
        image.compress(Bitmap.CompressFormat.PNG, 100, fos);
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return pictureFile;
}

private static File getOutputMediaFile(Context context){
    // To be safe, you should check that the SDCard is mounted
    // using Environment.getExternalStorageState() before doing this.
    File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
            + "/Android/data/"
            + context.getPackageName()
            + "/Files");

    // This location works best if you want the created images to be shared
    // between applications and persist after your app has been uninstalled.

    // Create the storage directory if it does not exist
    if (! mediaStorageDir.exists()){
        if (! mediaStorageDir.mkdirs()){
            return null;
        }
    }
    // Create a media file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.ENGLISH).format(new Date());
    File mediaFile;
    String mImageName="IMG_"+ timeStamp +".png";
    mediaFile = new File(mediaStorageDir.getPath() + File.separator + mImageName);
    return mediaFile;
}

当我打开文件并查看图像 DPI 信息时，它显示 72 像素/英寸 like this

如何将其设置为 300 像素/英寸或其他值？

Answer 1

这些是我在保存时将dpi设置为位图的方法，引用here还有here .

public void storeImage(Bitmap image) {
        try {
            File pictureFile = new File("yourpath");

            FileOutputStream fos = new FileOutputStream(pictureFile);


            ByteArrayOutputStream imageByteArray = new ByteArrayOutputStream();
            image.compress(Bitmap.CompressFormat.JPEG, 100, imageByteArray);
            byte[] imageData = imageByteArray.toByteArray();

            //300 will be the dpi of the bitmap
            setDpi(imageData, 300);

            fos.write(imageData);
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } 
    }


    public void setDpi(byte[] imageData, int dpi) {
        imageData[13] = 1;
        imageData[14] = (byte) (dpi >> 8);
        imageData[15] = (byte) (dpi & 0xff);
        imageData[16] = (byte) (dpi >> 8);
        imageData[17] = (byte) (dpi & 0xff);
    }