Save bitmap to file function

Here is the function which help you

private void saveBitmap(Bitmap bitmap,String path){
        if(bitmap!=null){
            try {
                FileOutputStream outputStream = null;
                try {
                    outputStream = new FileOutputStream(path); //here is set your file path where you want to save or also here you can set file object directly

                    bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream); // bitmap is your Bitmap instance, if you want to compress it you can compress reduce percentage
                    // PNG is a lossless format, the compression factor (100) is ignored
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    try {
                        if (outputStream != null) {
                            outputStream.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }    
        }
    }

Two example works for me, for your reference.

Bitmap bitmap = Utils.decodeBase64(base64);
try {
    File file = new File(filePath);
    FileOutputStream fOut = new FileOutputStream(file);
    bitmap.compress(Bitmap.CompressFormat.PNG, 85, fOut);
    fOut.flush();
    fOut.close();
}
catch (Exception e) {
    e.printStackTrace();
    LOG.i(null, "Save file error!");
    return false;
}

and this one

Bitmap savePic = Utils.decodeBase64(base64);
File file = new File(filePath);
File path = new File(file.getParent());

if (savePic != null) {
    try {
        // build directory
        if (file.getParent() != null && !path.isDirectory()) {
            path.mkdirs();
        }
        // output image to file
        FileOutputStream fos = new FileOutputStream(filePath);
        savePic.compress(Bitmap.CompressFormat.PNG, 90, fos);
        fos.close();
        ret = true;
    } catch (Exception e) {
        e.printStackTrace();
    }
} else {
    LOG.i(TAG, "savePicture image parsing error");
}

In kotlin :

private fun File.writeBitmap(bitmap: Bitmap, format: Bitmap.CompressFormat, quality: Int) {
    outputStream().use { out ->
        bitmap.compress(format, quality, out)
        out.flush()
    }
}

usage example:

File(exportDir, "map.png").writeBitmap(bitmap, Bitmap.CompressFormat.PNG, 85)

Edit: This was my original answer and its nice, but lately I use this:

fun File.createFileAndDirs() = apply {
    parentFile?.mkdirs()
    createNewFile()
}

fun File.write(
    bitmap: Bitmap, format: Bitmap.CompressFormat = Bitmap.CompressFormat.JPEG, quality: Int = 80
) = apply {
    createFileAndDirs()
    outputStream().use {
        bitmap.compress(format, quality, it)
        it.flush()
    }
}

It's better because there are some useful defaults in-place and also it creates file if it doesn't exist.

1. You need an appropriate permission in manifest.xml:

   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
   

2. out.flush() check the out is not null..

3. String file_path = Environment.getExternalStorageDirectory().getAbsolutePath() + 
                               "/PhysicsSketchpad";
   File dir = new File(file_path);
   if(!dir.exists())
       dir.mkdirs();
   File file = new File(dir, "sketchpad" + pad.t_id + ".png");
   FileOutputStream fOut = new FileOutputStream(file);
   
   bmp.compress(Bitmap.CompressFormat.PNG, 85, fOut);
   fOut.flush();
   fOut.close();