Question

I try to display image to the Screen at Retina iPhone.
So I used this code.

#define ScreenWidth 960
#define ScreenHeight 640

void ConvertCoordf(float* x, float* y)  
{  
    int height = ScreenHeight;  
    if ( height / 2 > *y )  
        *y += (height / 2 - *y) * 2;  
    else if ( height / 2 < *y )  
        *y -= (*y - height / 2) * 2;      
}

void DISPLAY_UPDATE(char *name, int x , int y , int startx, int starty , int w , int h ,float rotation)  
{  
    CCSprite *sprite = [[CCSprite spriteWithFile:[NSString stringWithUTF8String:name] rect:CGRectMake(startx, starty, w, h)] retain];  
    float drawX = x, drawY = y;   
    CGSize size = [sprite contentSize];

    int nWidth = size.width;
    int nHeight = size.height;
    drawX = drawX + nWidth/2;
    drawY = drawY - nHeight/2;

    ConvertCoordf(&drawX, &drawY);
    drawY -= nHeight;
    [sprite setPosition:ccp(drawX, drawY)];
    [sprite setAnchorPoint:CGPointMake(0.5, 0.5)];
    [sprite setRotation:rotation];
    [_mainLayer addChild:sprite];
    [sprite release];
}

Unfortunately, the image doesn’t display correctly.
The image’s position is wrong.
But in other iphone, it display correct.
What’s the matter?
What’s the problem in this coordinate convert?

Screenshots

Answer 1

This is completely wrong:

#define ScreenWidth 960
#define ScreenHeight 640

The correct values of these macros:

#define ScreenWidth 480
#define ScreenHeight 320

This is because you are not working with pixels. You are working with points and the system will calculate the pixels for you. This means the iPhone screen is always 480×320 points. You can also use pixels, but then you have to check the documentation.
Soon I will add here a link to the description of this problem in the documentation.

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Edit added documentation link: Points Versus Pixels