Scale transform in AffineTransformOp produces row/column of dead pixels

Question

Hello,
On JDK 1.4.1, both Windoze and Linux, the following code:
double aScaleFactor = ((double) finalSize) / aSourceSize;
AffineTransform aScaleTransform =
AffineTransform.getScaleInstance(aScaleFactor, aScaleFactor);
AffineTransformOp aScaleOp = new AffineTransformOp(aScaleTransform, anInterpolationType);
Rectangle aDestinationRegion =
aScaleOp.getBounds2D(sourceImage).getBounds();
aScaleOp.filter(sourceImage, destinationBuffer);
scaleIntoSubimage = destinationBuffer.getSubimage( aDestinationRegion.x, aDestinationRegion.y, aDestinationRegion.width, aDestinationRegion.height);
... works as expected, except that sometimes the last row (row of largest y) or last column (column of greatest x) does not get written into so the pixels are all 0.
Exactly when this happens depends on the precise size of the source image , and size of destination image. Usually, increasing the size of the destination image by just one pixel causes the aberration to disappear.
Is this a bug in the JDK? Some type of rounding error?
thanks for any pointers.
joe

Answer 1

I find the following code creates excellent quality thumbnails on Windows and Linux - and no X server required! Hope it helps - if there is a better way of getting rid of that line let me know!
import java.io.*;
import javax.imageio.*;
import java.awt.image.*;
import java.awt.geom.*;
public class Main
public Main(String srcFileName,String destFileName,int thumbNailSize) throws Exception
// Read in original image to create thumbnail from
File inFile = new File(srcFileName);
BufferedImage bufferedImage = ImageIO.read(inFile);
// Calculate scale so image fits in a square area of thumbNailSize - e.g. 160
int imageWidth = bufferedImage.getWidth();
int imageHeight = bufferedImage.getHeight();
int componentWidth = thumbNailSize;
int componentHeight = thumbNailSize;
double scale = -1;
if ( imageWidth == componentWidth && imageHeight == componentHeight)
scale = 1;
else if ( imageWidth <= componentWidth && imageHeight <= componentHeight)
// set scale to 1 if we don't want to scale up - otherwise use code below...
scale = 1;
// double heightScale = ((double)componentWidth) / ((double)imageWidth);
// double widthScale = ((double)componentHeight) / ((double)imageHeight);
// if ( heightScale < widthScale ) scale = heightScale;
// else scale = widthScale;
else if ( imageWidth > componentWidth && imageHeight <= componentHeight)
double heightScale = ((double)componentWidth) / ((double)imageWidth);
scale = heightScale;
else if ( imageWidth <= componentWidth && imageHeight > componentHeight)
double widthScale = ((double)componentHeight) / ((double)imageHeight);
scale = widthScale;
else
double heightScale = ((double)componentWidth) / ((double)imageWidth);
int scaledHeight = (int)(((double)imageHeight) * heightScale);
double widthScale = ((double)componentHeight) / ((double)imageHeight);
int scaledWidth = (int)(((double)imageWidth) * widthScale);
if ( scaledWidth <= componentWidth ) scale = widthScale;
else scale = heightScale;
// Now create thumbnail
AffineTransform affineTransform = AffineTransform.getScaleInstance(scale,scale);
AffineTransformOp affineTransformOp = new AffineTransformOp(affineTransform,null);
BufferedImage scaledBufferedImage = affineTransformOp.filter(bufferedImage,null);
// Now do fix to get rid of silly spurious line
int scaledWidth = (int)(Math.round(scale*bufferedImage.getWidth()));
int scaledHeight = (int)(Math.round(scale*bufferedImage.getHeight()));
int expectedWidth = (int)(imageWidth * scale);
int expectedHeight = (int)(imageHeight * scale);
if ( scaledWidth > expectedWidth || scaledHeight > expectedHeight )
scaledBufferedImage = scaledBufferedImage.getSubimage(
0,0,expectedWidth,expectedHeight);
// Now write out scaled image to file
ImageIO.write(scaledBufferedImage,"JPG",new File(destFileName));
public static void main(String[] args)
if ( args.length < 3 )
System.err.println("Usage: imageTest srcFile DestFile size");
System.exit(-1);
try
int size = 160;
try
size = Integer.parseInt(args[2]);
catch (NumberFormatException numberFormatException) {}
Main main1 = new Main(args[0],args[1],size);
catch (Exception exception)
System.out.println(exception);
exception.printStackTrace();
}