Using Sprite Sheets for Stationary Images

Posted by jflowers45, Posted on September 2, 2011

1 vote

If you want to actually run this code you'll want to Download the full demo package

Essentially, it shows a few tips for reducing memory usage using sprite sheets

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require "sprite"
require "rackSpriteSmall"
 
function cleanAll() 
        if (rows ~= nil) then 
                for i=1,6,1 do
                        if (rows[i] ~= nil) then 
                                rows[i]:removeSelf()
                                rows[i]=nil
                        end
                        if (spritesets ~= nil and spritesets[i] ~= nil) then
                                spritesets[i]=nil
                        end
                end
                rows=nil
        end
        if (racksheet ~= nil) then
                racksheet:dispose()     --similar to display object :removeSelf(), but for spriteSheets
                rackSheetData=nil
        end
        
        if(blackRectangleBG ~= nil) then
                blackRectangleBG:removeSelf()
                blackRectangleBG=nil
        end
end
 
function updateText(stateNum,stateDesc)
        oldX=stateNumTxt.x
        stateNumTxt.text="State " .. stateNum
        stateNumTxt:setReferencePoint(display.CenterLeftReferencePoint);
        stateNumTxt.x=oldX
        
        oldX=stateDescTxt.x
        stateDescTxt.text= stateDesc 
        stateDescTxt:setReferencePoint(display.CenterLeftReferencePoint);
        stateDescTxt.x=oldX
        
end
 
function drawRowsBadWay()
        rows={}
        for by=1,6,1 do 
                local rowFilename="rack/row" .. by .. ".png"
                local aRowImg = display.newImageRect(rowFilename,480,320); 
                rows[by]=display.newGroup()
                rows[by].x, rows[by].y = 240,160
                rows[by]:insert(aRowImg)
        end
end
 
function drawRowsGoodWay()
        rackSheetData = rackSpriteSmall.getSpriteSheetData()
        racksheet = sprite.newSpriteSheetFromData( "rackSpriteSmall.png", rackSheetData )
        
        spritesets={}
        rows={}
                
        for by=1,6,1 do
                spritesets[by] =sprite.newSpriteSet(racksheet, by, 1)
                sprite.add( spritesets[by], "row", 1, 1, 5200, 0 )
                rows[by]=sprite.newSprite(spritesets[by])
                rows[by].x, rows[by].y = 240,160
                
        end
end
 
function drawRectBadWay()
        blackRectangleBG=display.newImageRect("blackRectangle.jpg",480,320);  
        blackRectangleBG.alpha=0.7
        blackRectangleBG.x, blackRectangleBG.y=240,160
end
 
function drawRectGoodWay()
        blackRectangleBG = display.newRect(0,0,480,320)
        blackRectangleBG:setFillColor(0,0,0)    
        blackRectangleBG.alpha=0.7
        blackRectangleBG.x, blackRectangleBG.y=240,160
end
 
function renderState(stateNum)
        cleanAll()
        if (stateNum==1) then
                updateText(stateNum,"Start: Touch to proceed")
        elseif (stateNum==2) then
                updateText(stateNum,"Draw rack using 6 images - uses 6MB")
                drawRowsBadWay()
        elseif (stateNum==3) then
                updateText(stateNum,"Memory released")
        elseif (stateNum==4) then
                updateText(stateNum,"Sprite sheet uses 1MB instead of 6MB!")
                drawRowsGoodWay()
        elseif (stateNum==5) then
                updateText(stateNum,"Memory released")
        elseif (stateNum==6) then
                updateText(stateNum, "Black dither as image - takes 1.05MB")
                drawRectBadWay()
        elseif (stateNum==7) then
                updateText(stateNum,"Memory released")
        elseif (stateNum==8) then
                updateText(stateNum,"Black Dither as drawing object - adds <0.02MB memory!")
                drawRectGoodWay()
        end
        
        textGroup.parent:insert(textGroup)
        performance.group.parent:insert( performance.group ) 
        
        if (blackRectangleBG ~= nil) then
                blackRectangleBG.parent:insert(blackRectangleBG)
        end
        
end
 
 
 
 
function screenTouch( event )
        if "ended" == event.phase then
                currentState=currentState+1
                if (currentState==9) then
                        currentState=1
                end
                renderState(currentState)
        end
end
 
Runtime:addEventListener( "touch", screenTouch )
 
fps = require("fps")
performance = fps.PerformanceOutput.new();
performance.group.x, performance.group.y = 120,  15;
performance.alpha = 0.6; -- So it doesn't get in the way of the rest of the scene
 
 
stateNumTxt = display.newText( "State 1:Empty.", 55, 260, "Verdana-Bold", 14 )
stateNumTxt:setTextColor( 255, 255, 255) 
stateNumTxt:setReferencePoint(display.CenterLeftReferencePoint);
 
stateDescTxt = display.newText( "Empty - touch to proceed", 55, 280, "Verdana-Bold", 14 )
stateDescTxt:setTextColor( 255, 255, 255) 
stateDescTxt:setReferencePoint(display.CenterLeftReferencePoint);
 
textGroup=display.newGroup()
textGroup:insert(stateNumTxt)
textGroup:insert(stateDescTxt)
 
currentState=1
renderState(1)

Replies

Posted on Wed, 2012-02-15 06:52
#1
akao's picture
akao
User offline. Last seen 1 week 23 hours ago. Offline
Pro Developer
Joined: 25 Feb 2011

Thanks for this! I have always heard that sprite saves texture memory, I had no idea!!

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