问检查视网膜像素iOS的工具或技术？

EN

-(void)drawRect:(CGRect)rect
{
    UIView* rootView = <GET_YOUR_ROOT_VIEW>;

    //You will probably want to change rect so you don't get distortion 
    //This assumes that this view is the same size as the screen
    [rootView drawViewHierarchyInRect:CGRectMake(0,0,rect.size.width*8, rect.size.height*8, afterScreenUpdates:YES];

    CGContextRef cxt = UIGraphicsGetCurrentContext();

    //Assumes this is @2x retina.  You should check the contentScale to be sure
    //and change accordingly
    CGContextScaleCTM(ctx, 0.5, 0.5);

    //Since we made the screen shot be 8x bigger the pixels
    //on an @2x device are in increments of 4
    for (int x = 0; x < rect.size.width*8; x+=4)
    {
        //Draw a line at x to ctx
    }

    for (int y = 0; y < rect.size.height*8; y+=4)
    {
        //Draw a line at y to ctx
    }

}