creating alpha images in java
java, java-2d
Solution
Is this possible with the standard JRE system libraries?
Yes, it is possible and is pretty simple aswell. The code below produces this image (transparent png):
public static void main(String[] args) throws IOException {
int x = 50, y = 50, w = 300, h = 200;
// draw the "shadow"
BufferedImage img = new BufferedImage(400, 300, BufferedImage.TYPE_INT_ARGB);
Graphics g = img.getGraphics();
g.setColor(Color.BLACK);
g.fillRect(x + 10, y + 10, w, h);
// blur the shadow
BufferedImageOp op = getBlurredOp();
img = op.filter(img, null);
// draw the box
g = img.getGraphics();
g.setColor(Color.RED);
g.fillRect(x, y, w, h);
// write it to disk
ImageIO.write(img, "png", new File("test.png"));
}
private static BufferedImageOp getBlurredOp() {
float[] matrix = new float[400];
for (int i = 0; i < 400; i++)
matrix[i] = 1.0f/400.0f;
return new ConvolveOp(new Kernel(20, 20, matrix),
ConvolveOp.EDGE_NO_OP, null);
}
Which libraries would make this kind of operation simple?
I would say that it depends on your other use cases. For simple shapes like boxes and ovals I would go for the solution above, no library is needed.
Problem
I'm about to start work on a project which will generate some PNGs with alpha (gradients) and hoping to draw them programmatically within java. For (a simple) example, I would like to draw a box, add a drop-shadow and then save this to a PNG file which can then be overlayed on some other graphic. - Is this possible with the standard JRE system libraries? - which libraries would make this kind of operation simple? thanks.