1. image(img,0,0,width,height);

1. help novices to do what they want with easy to use funciton
2. make simple sketches more concise.

1. PImage myBg;
2. PImage myPlayer;
3. PImage myEnemy;
4. void setup(){
5.    loadAllMyImages();
6. }
7. 
   
8. void loadAllMyImages(){
9.     myBg = loadImage("my_bg.png");
10.     myPlayer = loadImage("my_player.png");
11.     myEnemy = loadImage("my_enemy.png");
12. }
13. 
    
14. void draw(){
15.     image(myBg, 0,0 , width, height);  
16.             // inside of loadAllMyImages() this "my_bg.png" may be 100x100 or may be 3000x2000 pixels large)
17.             // so resizing large image every frame will consume a lot of CPU and will drop your framerate
18. 
    
19.     image(myPlayer, 10,10, 64,64);
20.             // same problem here, image of player may be 2048x2048 and resizing it to 64x64 would again consume
21.             // your CPU and drop frame rate
22.     image(myEnemy, 200,200, 32,32);
23. }

1. PImage myBg;
2. PImage myPlayer;
3. PImage myEnemy;
4. void setup(){
5.    loadAllMyImages();
6. }
7. 
   
8. /**
   *  Loads AND RESIZED images
   */
   void loadAllMyImages(){
9.     myBg = loadImage("my_bg.png");
10.     myBg.resize(width, height); // match scree nsize
11. 
    
12.     myPlayer = loadImage("my_player.png");
13.     myPlayer.resize(64,64); // we know that player is alwasy 64x64
14. 
    
15.     myEnemy = loadImage("my_enemy.png");
16.     myEnemy.resize(32,32); // we decided that enemy will always be 32x32
17. }
18. 
    
19. void draw(){
20.     image(myBg, 0,0); // now this will be very quick, as the image is alredy right size
21.     image(myBg, width, height); // even this one will be same quick, becaue processing will know
22.                                           // that image size already is same as 'width' and 'height' and will not perform
23.                                           // any resizing
24. 
    
25.     image(myPlayer, 10,10, 64,64);  // we can still use this code, as no conversion happens if image is already 64x64
26.     image(myPlayer, 10,10); // but better to use this code. Then if you forget to resize something, it will 
27.                                     // be visible on screen straight away. And if you would have left the code above
28.                                     // then image will be anyways resized and you will not see that you forgot to 
29.                                     // resize the image. Only peformance will drop. 
30.           
31.             image(myEnemy, 200,200); // that's a right way
32. }

This code always evalutates to false, thus this line is redundant. 

loadImage() is a blocking call.

  while (picts[idx] == null)   delay(PAUSE);