Convert base64 string to Image in Java

Question

I have an image being sent to me through a JSON string. I want to convert that string into an image in my android app and then display that image.

The JSON string looks like this:

"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAVI..."

Note: I truncated the string with a ...

I've got a function that (I think) converts the string into an image. Am I doing this right?

public Bitmap ConvertToImage(String image){
    try{
        InputStream stream = new ByteArrayInputStream(image.getBytes());
        Bitmap bitmap = BitmapFactory.decodeStream(stream);                 
        return bitmap;  
    }
    catch (Exception e) {
        return null;            
    }
}

Then I try to display it on my android activity like this

String image = jsonObject.getString("barcode_img");         
Bitmap myBitmap = this.ConvertToImage(image);
ImageView cimg = (ImageView)findViewById(R.id.imageView1);

//Now try setting dynamic image
cimg.setImageBitmap(myBitmap);

However, when I do this, nothing shows up. I don't get any errors in the logcat. What am I doing wrong?

Thanks

score 55 · Accepted Answer · answered Jul 06 '13 at 19:53

55

I'm worried about that you need to decode only the base64 string to get the image bytes, so in your

"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAVI..."

string, you must get the data after data:image\/png;base64,, so you get only the image bytes and then decode them:

String imageDataBytes = completeImageData.substring(completeImageData.indexOf(",")+1);

InputStream stream = new ByteArrayInputStream(Base64.decode(imageDataBytes.getBytes(), Base64.DEFAULT));

This is a code so you understand how it works, but if you receive a JSON object it should be done the correct way:

Converting the JSON string to a JSON object.
Extract the String under data key.
Make sure that starts with image/png so you know is a png image.
Make sure that contains base64 string, so you know that data must be decoded.
Decode the data after base64 string to get the image.

answered Jul 06 '13 at 19:53

Jorge Fuentes González

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1

you rock! thanks for the substring at index of "," too... that part was mandatory. – user952342 Jul 06 '13 at 20:06
what imports should i use for this? – diego matos - keke Jan 22 '16 at 20:37
@diegomatos-keke this: http://developer.android.com/reference/java/io/InputStream.html this: http://developer.android.com/reference/java/io/ByteArrayInputStream.html and this: http://developer.android.com/reference/android/util/Base64.html – Jorge Fuentes González Jan 25 '16 at 11:40
@JorgeFuentesGonzález Can you please tell me what do I need to import? Thank you – Gregorius Edwadr Jan 29 '16 at 08:09
@GregoriusEdwadr The answer is the comment above your question. – Jorge Fuentes González Feb 01 '16 at 15:02

score 5 · Answer 2 · answered Jul 06 '13 at 19:42

5

InputStream stream = new ByteArrayInputStream(image.getBytes());

should be changed to

InputStream stream = new ByteArrayInputStream(Base64.decode(image.getBytes(), Base64.DEFAULT));

Refer http://developer.android.com/reference/android/util/Base64.html for details on how to do Base64 decoding.

Disclaimer: I have not checked for syntax, but this is how you should do it.

answered Jul 06 '13 at 19:42

Wand Maker

18,476
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@Jorge, Instead of downvoting, you could have edited my answer. Point is that the author was missing to perform base 64 decoding. – Wand Maker Jul 06 '13 at 19:57
Thanks Wand Maker! Your solution was half right... but I did need to take a substring as well after the ",". – user952342 Jul 06 '13 at 20:07

score 1 · Answer 3 · edited Dec 03 '14 at 19:19

Here is the working code that converts the Base64 encoded inputStream and writes it to the disk. I spent a few time to make it work correctly. So I hope this helps other developers.

public boolean writeImageToDisk(FileItem item, File imageFile) {
    // clear error message
    errorMessage = null;
    FileOutputStream out = null;
    boolean ret = false;
    try {
        // write thumbnail to output folder
        out = createOutputStream(imageFile);

        // Copy input stream to output stream
        byte[] headerBytes = new byte[22];
        InputStream imageStream = item.getInputStream();
        imageStream.read(headerBytes);

        String header = new String(headerBytes);
        // System.out.println(header);

        byte[] b = new byte[4 * 1024];
        byte[] decoded;
        int read = 0;
        while ((read = imageStream.read(b)) != -1) {
            // System.out.println();
            if (Base64.isArrayByteBase64(b)) {
                decoded = Base64.decodeBase64(b);
                out.write(decoded);
            }
        }

        ret = true;
    } catch (IOException e) {
        StringWriter sw = new StringWriter();
        e.printStackTrace(new PrintWriter(sw));
        errorMessage = "error: " + sw;

    } finally {
        if (out != null) {
            try {
                out.close();
            } catch (Exception e) {
                StringWriter sw = new StringWriter();
                e.printStackTrace(new PrintWriter(sw));
                System.out.println("Cannot close outputStream after writing file to disk!" + sw.toString());
            }
        }

    }

    return ret;
}

/**
 * Helper method for the creation of a file output stream.
 * 
 * @param imageFolder
 *            : folder where images are to be saved.
 * @param id
 *            : id of spcefic image file.
 * @return FileOutputStream object prepared to store images.
 * @throws FileNotFoundException
 */
protected FileOutputStream createOutputStream(File imageFile) throws FileNotFoundException {

    imageFile.getParentFile().mkdirs();

    return new FileOutputStream(imageFile);
}

Convert base64 string to Image in Java

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