How to Properly Scale a BufferedImage in Java: Resampling vs. Cropping?

Scaling a BufferedImage: Delving into Resampling, Not Cropping

Your attempt to scale a BufferedImage using the Graphics2D class may not yield the desired results due to the limitations imposed by the method. The scale() method simply transforms the current graphics context without modifying the underlying image data.

AffineTransformOp: The Preferred Solution for Resampling

For resampling, the AffineTransformOp class provides greater flexibility by allowing you to specify the interpolation type. Interpolation determines how intermediate pixel values are calculated when the image is scaled. Here's an example using AffineTransformOp to scale an image:

BufferedImage before = getBufferedImage(encoded);
int w = before.getWidth();
int h = before.getHeight();
BufferedImage after = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
AffineTransform at = new AffineTransform();
at.scale(2.0, 2.0);
AffineTransformOp scaleOp = new AffineTransformOp(at, AffineTransformOp.TYPE_BILINEAR);
after = scaleOp.filter(before, after);

In this example:

• AffineTransform is used to define the scaling transformation.
• AffineTransformOp is employed with the TYPE_BILINEAR interpolation type, which provides smooth and high-quality results.
• filter() applies the transformation and resamples the image into the after BufferedImage.

Key Points

• Use AffineTransformOp for resampling images, not cropping.
• Choose the appropriate interpolation type for optimal results, such as TYPE_BILINEAR.
• Refer to related resources for additional examples and insights into image scaling.

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