Is there a way to decode a .ICO file to a resolution bigger than 16x16?

问题

I'm working on android and trying to download and display a favicon(.ICO) from a website on an ImageView.

So far I've manage to read the .ico from a website using an HTTP connection, retrieve it as an InputStream. Then I use a BitmapFactory to decode the stream into a Bitmap and display it on the ImageView. Here's the code:

 public Bitmap getBitmapFromURL(URL src) {           
        try {

            URL url = new URL("http", "www.google.com", "/favicon.ico");

            HttpURLConnection connection = (HttpURLConnection) url.openConnection();                

            connection.setDoInput(true);       

            connection.connect();               

            InputStream input = connection.getInputStream();    

            BitmapFactory.Options options = new BitmapFactory.Options();

            Bitmap myBitmap = BitmapFactory.decodeStream(input, null, options);  

            return myBitmap;

        } catch (IOException e) {               
            e.printStackTrace();                
            return null;                
        }
    }

The problem is that the decoding of the inputStream always returns a small 16x16 Bitmap. If I well understood, a single .ICO file can store different image resolutions, like 32x32 and 64x64. My question is, is there a way to decode the 32x32 or the 64x64 Bitmap instead of the 16x16?

Also, if there isn't a solution with BitmapFactory, is there a library or java code to do this?

NOTE: I don't want to resize the Bitmap, I want a 32x32(or bigger) resolution without losing the image quality by stretching.

Thanks in advance.

回答1:

I know the question was asked 3 years ago, but I have faced the very same problem and adapted a portion of image4j into ico4a, which you can find here: https://github.com/divStar/ico4a (I wrote it myself because I wanted to load the biggest image from a favicon; since image4j uses AWT-classes, which are not easily available for android, I made it so ico4a mostly uses native android classes).

It can decode most valid ICO-files into a List of Bitmap-objects. I believe either the library itself or the sample application has also a method to retrieve the biggest Bitmap-object.

However, my library is not able to write ICO-files; it can only read them. You can save the individual images as PNG or JPEG graphics easily though using some built-in android functionality.

回答2:

The favicon file may contains mutliple icons, usually one in 16x16 and one in 32x32. This is discussed in the following thread : How to have multiple favicon sizes, yet serve only a 16x16 by default?

It is the case with the Google's favico. If you try to download the file www.google.com/favicon.ico and open it with an application like IrfanView, you can see that there are two icons (16x16 and 32x32).

To answer your question, you should use a proper library to extract multiple icons, like image4j, and choose the one you need.

http://image4j.sourceforge.net/

来源：https://stackoverflow.com/questions/18678848/is-there-a-way-to-decode-a-ico-file-to-a-resolution-bigger-than-16x16

标签

java

android

bitmap

ico