set a color to transparent

Java 2D
#1

Hi, well I have a BufferedImage (Sprite) and want to set the background color transparent…
I use this code


public class Transparency 
{
  	public static BufferedImage makeColorTransparent(BufferedImage im, final Color color)
  	{
    	ImageFilter filter = new RGBImageFilter()
    	{
      		public int markerRGB = color.getRGB() | 0xFF000000;

      		public final int filterRGB(int x, int y, int rgb)
      		{
        		if ( ( rgb | 0xFF000000 ) == markerRGB )
        		{
          			return 0x00FFFFFF & rgb;
          		}
        		else
        		{
          			return rgb;
          		}
        	}
    	}; 

    ImageProducer ip = new FilteredImageSource(im.getSource(), filter);
    
    Image src = Toolkit.getDefaultToolkit().createImage(ip);

	BufferedImage jo = new BufferedImage(src.getWidth(null), src.getHeight(null), BufferedImage.TYPE_INT_ARGB);
	Graphics2D g2 = jo.createGraphics();
	g2.drawImage(src, 0, 0, null);
	g2.dispose();

    return jo;
    }
    
}

It was actually made so that it puts out awt.Image but I need BufferedImage, so I changed it this way…

But if Images are bigger its a bit laggy because I use this, I believe:


    Image src = Toolkit.getDefaultToolkit().createImage(ip);

	BufferedImage jo = new BufferedImage(src.getWidth(null), src.getHeight(null), BufferedImage.TYPE_INT_ARGB);
	Graphics2D g2 = jo.createGraphics();
	g2.drawImage(src, 0, 0, null);
	g2.dispose();

thats because you cannot simply cast an Image to BufferedImage…

or is there a faster possibility ?

#2

Eh… just use some image format, which supports transparency like gif or png.

#3

or if you must do it with colours, then why not just:

for(bla bla loop y) {
 for(bla bla loop x) {
  if(image.getRgb(x,y) blabla is the colour) image.setRgb(x,y,0x00000000);
 }
}
#4

ya I have to do it this way… I have > 1000 bmp pics with black background…


		for(int y=0;y < pic.getHeight();y++)
		{
 			for(int x=0;x < pic.getWidth();x++)
 			{
  				if(pic.getRGB(x,y) == new Color(0,0,0)) {pic.setRGB(x,y,0x00000000);}
  			}
		}

this doesn’t work because getRGB(x,y) returns an integer… but how to describe a color with it ?
if the color is black, 0,0,0 pure black, he should replace this with transparency what hopefully 0x00000000 represents… but whats how looks black then ? ^^

#5

in an image with type INT_ARGB, black is 0xFF000000
each pixel is an integer of the form 0xAARRGGBB

#6

apprently the type of the BufferedImage is mostly 13 and sometimes 6, well how to say the BufferedImage to be INT_ARGB ?
there is no setType Method and the construktor requires width, height along with a type, but the size is different… so I cannot say that

#7 

 		BufferedImage transpic = new BufferedImage(pic.getWidth(), pic.getHeight(),BufferedImage.TYPE_INT_ARGB);
		
		Graphics2D g = (Graphics2D) transpic.getGraphics();
                           g.drawImage(pic, 0, 0, null);
		
		for(int y=0;y < transpic.getHeight();y++)
		{
 			for(int x=0;x < transpic.getWidth();x++)
 			{
  				if(transpic.getRGB(x,y) == 0xFF000000) {transpic.setRGB(x,y,0x00000000);}
  			}
		}

know getType() really is TYPE_INT_ARGB but it doesn’t matter, I can replace with any color, but not with none… which means the Alpha Value in 0xAARRGGBB does not work :frowning:

#8

what doesn’t work? what happens? what goes wrong?
“doesn’t work” is one of the most undescriptive things you can say :wink:

#9 
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;

public class BlackTrans{
	public static void main(String[]args)throws Exception{
		BufferedImage in=ImageIO.read(BlackTrans.class.getResourceAsStream("/blacktrans.png"));
		BufferedImage out=new BufferedImage(in.getWidth(),in.getHeight(),BufferedImage.TYPE_INT_ARGB);
		Graphics g=out.getGraphics();
		g.drawImage(in,0,0,null);
		g.dispose();
		for(int x=out.getHeight()-1;x>=0;--x){
			for(int y=out.getWidth()-1;y>=0;--y){
				if(out.getRGB(x,y)==0xff000000)
					out.setRGB(x,y,0);
			}
		}
		ImageIO.write(out,"png",new File("blacktransout.png"));
	}
}

Works just fine.

edit: You should do that offline… and not on startup.

#10

here’s some information on ARGB data with AWT, though I don’t use that at all to set transparent colors but I simply do get the pictures transformed by a common Graphical Program like the GIMP.