[gullet]

Hi,

I need to display text to explain details on a map. So I guess that I would go for text-based Sprites, but that will look ugly if I don't use transparent images for the sprites.

My idea is to :

1. Take the text (mostly short texts) and calculate its dimension from the font and text
2. Create an image with the width and height of the text
3. Create an int[] of the size of the image
4. Fill the int[] with 0xAARRGGBB values
5. Change the color to the text color
6. drawString to display the text
7. Create the sprite from the image

I have googled my brains out for some information regarding text-based sprites, but I haven't found anything. Is it the wrong approach? I'm struggling a bit here, so any help is appreciated.

Thanks in advance.

[grahamhughes]

Essentially, there is no MIDP mechanism for doing what you want, since you cannot create a mutable Image (one you can draw on) where the pixels are transparent.

You have three options.

1. You can do what you want on Nokia devices. Nokia provide an extension API that gives you extra options for creating mutable Image objects. Take a look at the method in the class com.nokia.mid.ui.DirectUtils. Downsides: Nokia and possibly Sony Ericsson only. May not work on some Series 60s.

2. Don't use an Image. Just draw the text where you want it. Downside: drawing text may be slower than drawing an Image.

3. Create a mutable Image with opaque pixels, using Image.createImage(width, height). Draw text on it, in a different colour to the background. Use getRGB() to acquire the pixel data in an int[]. Change all the background colour pixels to transparent, then convert the array back to an Image using Image.createRGBImage(). Downsides: may be slow to do this; pixel arrays can consume a lot of memory (though, your images are probably small); may have unpleasant results on devices with anti-aliased fonts.

Cheers,
Graham.

[gullet]

Graham,

Thanks for your tips! I went with the third option. It works great, but I have yet to see the performance hit for the "transparency loop".

Thanks!