Drawing blocks for a 2D game background

Question

This draws blocks on the screen from a grid to make a background for my game. I am wondering if anyone has any suggestions on optimizing it for speed.

int blockwidth=blocksize-2;
//Draw coloured blocks
for (int x=0;x<sizex;x++){
   int screenx=-(int)camerax+(x*blocksize);
      if (screenx>-blocksize && screenx<gamewidth){
        for (int y=0;y<sizey;y++){
          int screeny=-(int)cameray+(y*blocksize);    
          if (screeny>-blocksize && screeny<gameheight){              
            if (tiles[x][y][0]>0){
                g.setColor(new Color( tiles[x][y][1]));
                //g.fillRect(screenx,screeny,blockwidth,blockwidth); 
                g.drawImage(Iloader.Imagelist.get(0), screenx,screeny, screenx+blockwidth,screeny+blockwidth, graphicsize,0,graphicsize*2,graphicsize, null);
            } else {
                //g.setColor(new Color( tiles[x][y][1]  | 0xFFFF0000));
                g.setColor(new Color( tiles[x][y][1]));
                g.fillRect(screenx,screeny,blockwidth,blockwidth);   

            }
          }
        }
    }
 } 

Answer 1

There are a few optimizations I can see in your code.

1. creating a new Color every time is a little severe. You can do a few things here, for example, if your color palette is limited, then cache the individual Color instances. I know it sounds petty right now, but, when you add it up there are a lot of new Color instances created.

   What you should at minimum do, is track your last Color used, and only create a new one if it is different.

2. Pull the Iloader.Imagelist.get(0) outside the loop, and have Image image = Iloader.Imagelist.get(0)

3. Pull calculations outside the loops where you can... and continue/break when you can too.

   Image image = Iloader.Imagelist.get(0);
   int screenx=-(int)camerax - blocksize;
   for (int x = 0; x < sizex; x++){
       screenx += blocksize;
       if (screenx <= -blocksize) {
           continue;
       }
       if (screenx >= gamewidth) {
           break;
       }
       int screeny= -(int)cameray - blocksize;
       for (int y = 0; y < sizey; y++){
           screeny += blocksize;
           if (screeny <= -blocksize)
               continue;
           }
           if (screeny >= gameheight) {
               break;
           }              
           if (tiles[x][y][0] > 0) {
               // need to set the color here? g.setColor(new Color( tiles[x][y][1]));
               g.drawImage(image, screenx, screeny, screenx + blockwidth,
                           screeny + blockwidth, graphicsize, 0, graphicsize * 2,
                           graphicsize, null);
           } else {
                   //g.setColor(new Color( tiles[x][y][1]  | 0xFFFF0000));
               g.setColor(new Color( tiles[x][y][1]));
               g.fillRect(screenx,screeny,blockwidth,blockwidth);   
   
           }
       }
   }
   

The above code does not have the mechanism for caching the color. You should figure one out.