Error Image.getColor(x,y) and error FPS in SLICK AE

[reben]

Hi guys! I'm working on a project with Slick and SlickAE and I have two problems. The first is that my game is very fast because there will always 60FPS. I've tried with setTargetFrameRate(20) but does not work. I have also tried to make a Thread.sleep(x) and I got down to 20 fps, but and I got down to 20 frames. I have also tried to put a counter and also slows down but continues to go very fast. Do not know what to do :S

The other thing is that I travel a 20x20 image and get the color of each pixel to change its color if necessary, but when you run the code I get this error: Fail: Unsupported: glGetTexImage and 20x20 image is painted as a black square

import org.newdawn.slick.Image;

public class PlayerPaint {

    img = new Image("player.png");
    private Color oneColor = new Color(255, 255, 0);

    public synchronized void update(boolean alt) throws SlickException {
        Color c0, c1;
        ImageBuffer buff = new ImageBuffer(20, 20);
      for (int x = 0; x < 20; x++) {
         for (int y = 0; y < 20; y++) {
                           c0 = img.getColor(x, y);
                           if(c0.equals(oneColor))
                               c1 = oneColor;
                           if (c1 != null) {
            buff.setRGBA(x, y, c1.getRed(), c1.getGreen(), c1.getBlue(), c1.getAlpha());
                        }
                 }
        img = buff.getImage();
    }
}

I also tried with c0 = img.getGraphics (). GetPixel (x, y) instead of c0 = img.getColor (x, y) but does not work
I also tried libgdx (slickAE base) with this code and now if they are out silhouettes of players but strangely colored and transparent and filled areas where they should not. How could I? Thxxx

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Pixmap;
import org.newdawn.slick.Color;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.SlickException;

public class PlayerPaint {
    public synchronized void update(boolean alt) throws SlickException {
        Pixmap imgPix = new Pixmap(Gdx.files.internal("player.png"));
        Image image;
        private Color oneColor = new Color(255, 255, 0);
        Color newColor;
        ImageBuffer buff = new ImageBuffer(20, 20);
        for (int x = 0; x < 20; x++) {
           for (int y = 0; y < 20; y++) {
                    newColor = new Color(imgPix.getPixel(x, y));
                    if(newColor.equals(oneColor))
                        buff.setRGBA(x, y, oneColor.getRed(), oneColor.getGreen(), oneColor.getBlue(), oneColor.getAlpha());
                    else
                        buff.setRGBA(x, y, 0, 0, 0, 0);
            }
        }
        image = buff.getImage();
    }
  
    public void paint(int x, int y, Graphics g) {
    g.drawImage(image, x, y);
    }
}