Transitioning Colours

[Mikpo Siru]

Hi,

I have written a class that transitions from a starting colour to and ending colour. However there is one problem: the ending colour is always slightly off from what I specify. I've done my best to take care of rounding errors...any hints as to how I should proceed?

Thanks.

class ColourTransitioner implements Runnable{
        Color start;
        Color end;
        int steps;
        int timems;
        float redStep, grnStep, bluStep, aStep;
        Color curColour;
        
        public ColourTransitioner(Color startColour, Color endColour, int totalTransitionTime, int transitionSteps){
            this.start = start;
            this.end = end;
            this.steps = transitionSteps;
            this.timems = totalTransitionTime;
            calculateArgbSteps();
            curColour= start;
        }
        
        @Override
        public void run(){
            int newr = curColour.getRed();
            int newg = curColour.getGreen();
            int newb = curColour.getBlue();
            int newa = curColour.getAlpha();
            
            while(steps > 0){
                curColour= new Color(newr, newg, newb, newa);
                myJpanel.setBackground(curColour);    //This is the component whose colour is being changed
                repaint();
                steps--;
               
                try{
                    Thread.sleep(timems);
                } catch(InterruptedException e){
                }
                
                newr = (int)(curColour.getRed() + redStep);
                newg = (int)(curColour.getGreen() + grnStep);
                newb = (int)(curColour.getBlue() + bluStep);
                newa = (int)(curColour.getAlpha() + aStep);
            }
        }
        
        private void calculateArgbSteps(){
            redStep = (end.getRed() - start.getRed())/(float)steps;
            grnStep = (end.getGreen() - start.getGreen())/(float)steps;
            bluStep = (end.getBlue() - start.getBlue())/(float)steps;
            aStep = (end.getAlpha() - start.getAlpha())/(float)steps;
            timems = (int)(timems/(float)steps);
        }
    }

[Mikpo Siru]

Just thought of a crude way around it: when colour transition loop finishes, force the final colour to be the given ending colour. However the discontinuity in colour is obvious. Other suggestions are welcome!

[Mikpo Siru]

Fixed it by performing the step calculations in the loop.

    class ColourTransitioner implements Runnable{
        Color start;
        Color end;
        int steps;
        int timems;
        float redStep, grnStep, bluStep, aStep;
        
        public ColourTransitioner(Color start, Color end, int timems, int steps){
            this.start = start;
            this.end = end;
            this.steps = steps;
            this.timems = (int)(timems/(float)steps);;
        }
        
        @Override
        public void run(){
            Color newCol;
            int newr, newg, newb, newa;
            int curStep = 0;
            
            while(curStep < steps){
                newr = start.getRed() + (int)(curStep * ((end.getRed() - start.getRed())/(float)steps));
                newg = start.getGreen() + (int)(curStep * ((end.getGreen() - start.getGreen())/(float)steps));
                newb = start.getBlue() + (int)(curStep * ((end.getBlue() - start.getBlue())/(float)steps));
                newa = start.getAlpha() + (int)(curStep * ((end.getAlpha() - start.getAlpha())/(float)steps));
                
                newCol = new Color(newr, newg, newb, newa);
                
                myJpanel.setBackground(newCol);    //This is the component whose colour is being changed
                repaint();
                curStep++;
               
                try{
                    Thread.sleep(timems);
                } catch(InterruptedException e){
                }
            }
        }
    }