Drawing on image in res folder

[jules_]

Hi,

I am fairly new to the graphics side of things and was wondering how I can draw on an image which is in my res folder. My current code is :

Image im = Image.createImage("/imagefromresfolder.png");
drawdots(im,xco,yco);//xco,xyco are ints but not relevant to this example

public void drawdots(Image img, int x, int y) {

img.getGraphics().setColor(0xFF0000);
img.getGraphics().drawLine(0, 0, 100, 100);
}

I get an illegal state exception which leads me to believe that I am unable to get the graphics and manipulate images in this way. I would greatly appreciate any help. Many thanks

Jules

[grahamhughes]

Image objects are either "mutable" (you can draw on them) or "immutable" (you cannot draw on them).

You can find out which kind of image you have, using the isMutable() method. If this returns true, then getGraphics() will return a Graphics object. If false, then getGraphics() will throw an IllegalStateException.

Images created from a resource file are always immutable. You can check the JavaDocs for the kind of Image returned from each method.

The only way to create a mutable Image is to use createImage(width,height). This creates an image, in which all the pixels are white.

You can:

public static Image createMutableImage(String filename) throws IOException {
    Image imgResource = Image.createImage(filename);
    Image imgToDrawOn = Image.createImage(imgResource.getWidth(), imgResource.getHeight());
    Graphics g = imgToDrawOn.getGraphics();
    g.drawImage(imgResource, 0, 0, Graphics.TOP | Graphics.LEFT);
    return imgToDrawOn;
}

However, since the mutable image starts with all white pixels, if the resource-image you draw on it contains any transparent pixels, the original white pixels will show through. As a result, you cannot create a mutable image in which any pixels are transparent.

(You can create a mutable image with transparent pixels by using the Nokia UI API, but you will be unable to use your code on non-Nokia devices.)

Graham.

[jules_]

Thanks for the reply.

I'll give it a go shortly and post my results.

Jules

[jules_]

Hi

That worked perfectly. Thank you again.

Jules

[Tiger79]

yay ! Graham scores ! .... again....