How to Fit an Image to the Screen Size

If we want to use an image as background in a J2ME application, we have the problem that we must to have one image for each different size screen. Another approach is to have only one image and fit it to all screen sizes.

In this article I will describe an algorithm to do that.

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Method Name
CreateScaledImage
Parameters
imgOldImage	Image that we have to fit
iNewWidth	The new witdth of the image
iNewHeight	The new height of the image
Return Value
New image with the new size

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This is the algorithm:


public static Image CreateScaledImage( Image imgOldImage, int iNewWidth, int iNewHeight )
{

Image imgNewImage = null;
final int iOldWidth = imgOldImage.getWidth();
final int iOldHeight = imgOldImage.getHeight();

int iOldRGBArray[] = new int[iOldWidth * iOldHeight];

imgOldImage.getRGB( iOldRGBArray, 0, iOldWidth, 0, 0, iOldWidth, iOldHeight);

int iNewRGBArray[] = new int[iNewWidth * iNewHeight];

for (int yy = 0; yy < iNewHeight; yy++)
{
int dy = yy * iOldHeight / iNewHeight;

for (int xx = 0; xx < iNewWidth; xx++)
{
int dx = xx * iOldWidth / iNewWidth;

iNewRGBArray[(iNewWidth * yy) + xx] = iOldRGBArray[(iOldWidth * dy) + dx];
}
}

imgNewImage = Image.createRGBImage(iNewRGBArray, iNewWidth, iNewHeight, true);

return imgNewImage;

}


Then we have to use this method in a Canvas Object in this way:


public class MyCanvas extends GameCanvas
{
private Image objBKGImage = null;

public void paint(Graphics g)
{

iViewH = this.getHeight();
iViewW = this.getWidth();

// load the background image
if (objBKGImage== null)
{
try {
objBKGImage = Image.createImage("/res/Logo_150_53.png");
objBKGImage = CreateScaledImage(objBKGImage, iViewW, iViewH)
} catch (IOException ex) {
ex.printStackTrace();
}
}

// draw background
if (objBKGImage!= null)
g.drawImage(objBKGImage,
(int)iViewW / 2,
(int)iViewH / 2,
Graphics.VCENTER | Graphics.HCENTER );

}
}