How to scale a BufferedImage

Question

Following the javadocs, I have tried to scale a BufferedImage without success here is my code:

BufferedImage image = MatrixToImageWriter.getBufferedImage(encoded); Graphics2D grph = image.createGraphics(); grph.scale(2.0, 2.0); grph.dispose(); 

I can't understand why it is not working, any help?

Answer 1

AffineTransformOp offers the additional flexibility of choosing the interpolation type.

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); 

The fragment shown illustrates resampling, not cropping; this related answer addresses the issue; some related examples are examined here.

Answer 2

Unfortunately the performance of getScaledInstance() is very poor if not problematic.

The alternative approach is to create a new BufferedImage and and draw a scaled version of the original on the new one.

BufferedImage resized = new BufferedImage(newWidth, newHeight, original.getType()); Graphics2D g = resized.createGraphics(); g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,     RenderingHints.VALUE_INTERPOLATION_BILINEAR); g.drawImage(original, 0, 0, newWidth, newHeight, 0, 0, original.getWidth(),     original.getHeight(), null); g.dispose(); 

newWidth,newHeight indicate the new BufferedImage size and have to be properly calculated. In case of factor scaling:

int newWidth = new Double(original.getWidth() * widthFactor).intValue(); int newHeight = new Double(original.getHeight() * heightFactor).intValue(); 

EDIT: Found the article illustrating the performance issue: The Perils of Image.getScaledInstance()