Swing/AWT/SWT :: Convolution And Gray Scale Filter

I implemented the gray scale filter and the convolution filter . If I apply before the grayscale filter convolution and then I can not see the picture, I see pretty much the JPanel that should contain the image. The two filters separately functioning correctly

Code filter grey scale

public BufferedImage greyScale(BufferedImage originalImage) {
BufferedImage destImg = new BufferedImage(originalImage.getWidth(), originalImage.getHeight(), BufferedImage.TYPE_INT_ARGB);
int alpha, red, green, blue;
for (int x = 0; x < originalImage.getWidth(); x++) {
for (int y = 0; y < originalImage.getHeight(); y++) {
int pixel = originalImage.getRGB(x, y);

[code]....