Monkey-X - Drawing in Images(WritePixels) in real time - code example

In the game Space Invaders there are blocks that can slowly be destroyed by the lasers. To do this in Monkey you must create a pixel array and modify the pixels inside and then create an image from the array. In this code I have created a method that draws rectangles/filled circles inside an image and the result is drawn on the screen. The image gets restored at random intervals. You can also create destructable terrain with that.

In the drawr and drawo methods there is a line that copies the sprite array inside the image. If you take that out and use this line after drawing a lot in the spriterarray the results will be faster.

Code below :

Import mojo

Global blockwidth:Int=256
Global blockheight:Int=256

Class block
    Field x=640/2-blockwidth/2
    Field y=480/2-blockheight/2
    Field image:Image
    Field pixels:Int[blockwidth*blockheight]
    Method resetimage()
        For Local i:Int = 0 Until blockwidth * blockheight
            b.pixels[i] = $FFFF0000
        Next
        image.WritePixels(b.pixels, 0, 0, blockwidth, blockheight, 0)
    End Method
    Method drawr(x1,y1,w1,h1,col)
        For Local y2=y1 Until y1+h1
        For Local x2=x1 Until x1+w1
            Local pc = y2*blockwidth+x2
            If pc >= 0 And pc < blockwidth*blockheight
                pixels[pc] = col
            End If
        Next
        Next
        b.image.WritePixels(b.pixels, 0, 0, blockwidth, blockheight, 0)
    End Method 
    Method drawo(x1,y1,radius,col)
        For Local y2=-radius To radius
        For Local x2=-radius To radius
            If (y2*y2+x2*x2) <= radius*radius+radius*0.8
                Local x3 = x2+x1
                Local y3 = y2+y1
                Local pc = y3*blockwidth+x3
                If pc>=0 And pc < blockwidth*blockheight
                    pixels[pc] = col
                End If
            End If
        Next
        Next    
        b.image.WritePixels(b.pixels, 0, 0, blockwidth, blockheight, 0)
    End Method
End Class    

Global b:block = New block

Class MyGame Extends App    
    Method OnCreate:Int()
        Seed = Rnd(1000)
        SetUpdateRate(60)
        b.image = CreateImage(blockwidth, blockheight)        
        b.resetimage
    End Method
    Method OnUpdate()
        Select Int(Rnd(1,3))
            Case 1
                b.drawr Rnd(-5,blockwidth),Rnd(-5,blockheight),Rnd(5,15),Rnd(5,15),$FF000000
            Case 2
                b.drawo Rnd(-5,blockwidth),Rnd(-5,blockheight),Rnd(5,10),$FF000000
        End Select
        If Int(Rnd(0,70)) = 1 Then b.resetimage
    End Method
    Method OnRender:Int()
        Cls
        DrawImage b.image, b.x,b.y
        SetColor 255,255,255
        DrawText "Drawing in images in realtime.",0,0
    End Method    
End Class

Function Main:Int()
    New MyGame()
End Function