98

There is already question like this link on StackOverflow and the accepted answer is "casting":

Image image = ImageIO.read(new File(file));
BufferedImage buffered = (BufferedImage) image;

In my program I try:

final float FACTOR  = 4f;
BufferedImage img = ImageIO.read(new File("graphic.png"));
int scaleX = (int) (img.getWidth() * FACTOR);
int scaleY = (int) (img.getHeight() * FACTOR);
Image image = img.getScaledInstance(scaleX, scaleY, Image.SCALE_SMOOTH);
BufferedImage buffered = (BufferedImage) image;

Unfortunatelly I get run time error:

sun.awt.image.ToolkitImage cannot be cast to java.awt.image.BufferedImage

Obviously casting does not work.
Question is: What is (or is there) the proper way of converting Image to BufferedImage?

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7
  • if you want to scale buffered image, try this try this [stackoverflow.com/questions/4216123/… [1]: stackoverflow.com/questions/4216123/… Commented Nov 28, 2012 at 12:41
  • 8
    For the record, it is NOT the compiler that is saying that. You are actually seeing a runtime error ... not a compilation error. Commented Nov 28, 2012 at 12:42
  • 1
    You are right. Thanks for pointing this out. I will edit question accordingly. Commented Nov 28, 2012 at 12:46
  • @user902383 Even if they are not answering my question directly - those are great solutions as well. Commented Nov 28, 2012 at 14:41
  • Small Thing to OP: Method ImageIO.read(File) returns a BufferedImage by its signature. (Reference) There is no need to first assign to an Image variable then cast to type BufferedImage. That might confuse people reading your code. Commented Aug 8, 2013 at 15:33

4 Answers 4

Reset to default
156

From a Java Game Engine:

/**
 * Converts a given Image into a BufferedImage
 *
 * @param img The Image to be converted
 * @return The converted BufferedImage
 */
public static BufferedImage toBufferedImage(Image img)
{
    if (img instanceof BufferedImage)
    {
        return (BufferedImage) img;
    }

    // Create a buffered image with transparency
    BufferedImage bimage = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_ARGB);

    // Draw the image on to the buffered image
    Graphics2D bGr = bimage.createGraphics();
    bGr.drawImage(img, 0, 0, null);
    bGr.dispose();

    // Return the buffered image
    return bimage;
}
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9 Comments

@SriHarshaChilakapati You shouldn't be worrying about the memory when using Java. Judging from average memory consumption by Java applications, other developers definitely don't worry about memory a little bit.
@TomášZato It seemed to me that you were from the C++ world, thinking to reuse the memory of the pixels of the image data. I mean by my previous comment that there is no need to worry about the memory in this case, as the GC will take care of it in Java.
@SriHarshaChilakapati So garbage collectors don't consume any resources? GC only saves you from the code surrounding memory. It doesn't eradicate a hardware limit.
This won't work if Image is not loaded yet, since getWidth(null) or getHeight(null) will return -1 in the case
I had to use BufferedImage.TYPE_INT_RGB instead of ARGB to get the colours of my thumbnail right
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22

One way to handle this is to create a new BufferedImage, and tell it's graphics object to draw your scaled image into the new BufferedImage:

final float FACTOR  = 4f;
BufferedImage img = ImageIO.read(new File("graphic.png"));
int scaleX = (int) (img.getWidth() * FACTOR);
int scaleY = (int) (img.getHeight() * FACTOR);
Image image = img.getScaledInstance(scaleX, scaleY, Image.SCALE_SMOOTH);
BufferedImage buffered = new BufferedImage(scaleX, scaleY, TYPE);
buffered.getGraphics().drawImage(image, 0, 0 , null);

That should do the trick without casting.

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4 Comments

Don't ever forget to dispose created graphics instances
How to "dispose created graphics interfaces"?
Should the type in the BufferedImage constructor match the one in the getScaledInstance?
No, the TYPE is something like ARGB or RGBA, the way the image data is stored internally - choose what feels most naturally to your application ; Just look into your Autocomplete when typing BufferedImage.[Autocomplete] to see all choices
4

If you use Kotlin, you can add an extension method to Image in the same manner Sri Harsha Chilakapati suggests.

fun Image.toBufferedImage(): BufferedImage {
    if (this is BufferedImage) {
        return this
    }
    val bufferedImage = BufferedImage(this.getWidth(null), this.getHeight(null), BufferedImage.TYPE_INT_ARGB)

    val graphics2D = bufferedImage.createGraphics()
    graphics2D.drawImage(this, 0, 0, null)
    graphics2D.dispose()

    return bufferedImage
}

And use it like this:

myImage.toBufferedImage()
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Comments

3

If you are getting back a sun.awt.image.ToolkitImage, you can cast the Image to that, and then use getBufferedImage() to get the BufferedImage.

So instead of your last line of code where you are casting you would just do:

BufferedImage buffered = ((ToolkitImage) image).getBufferedImage();
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1 Comment

1) It is frowned upon to use classes from the sun package. They are not guaranteed to be available in non-Oracle JDKs. 2) Method getBufferedImage() only works if the buffered image has been generated internally by TookitImage. Most often (99%) it is not, so the return value is null. Source Reference

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