Question

我想使用几个CALayers作为UIViewController的子层。第一个是背景。

其他人都在这个背景之前。

如何组合/绘制带孔/透明点的图像并在CALayer中绘制，以便背景仍然可见。

我不想为每张图片使用CALayer，最终会有20 000个CALayer或更多......

那么如何在CALayer中整理图像的“图像”？（然后用作子图层）

代码示例：

// rootView which is a UIViewController
- (void)viewDidLoad
{
    [super viewDidLoad];

    _sproutLayer = [[CGSproutLayer alloc] initWithLayer:[CALayer layer]];
    [self.view.layer addSublayer:_sproutLayer];
    [_sproutLayer setZPosition:1];
    [_sproutLayer setNeedsDisplay];

    _backgroundLayer = [[CALayer alloc] init];
    CGRect positionOne = CGRectMake(100, 100, 150, 150);
    _backgroundLayer.frame = positionOne;
    _backgroundLayer.backgroundColor = [UIColor blueColor].CGColor;
    _backgroundLayer.name = @"One";
    _backgroundLayer.contents = (id) [UIImage imageNamed:@"background.png"].CGImage;
    [self.view.layer addSublayer:_backgroundLayer];
    [_backgroundLayer setZPosition:0];
    [_backgroundLayer setNeedsDisplay];

    _refreshTimer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(doIterate:) userInfo:nil repeats:YES];
}

- (void)doIterate:(NSTimer *)timer
{    
    [self.something doComputeStuff];
    ...
    [_sproutLayer draw];
}

// CGSproutLayer which is a CALAyer
- (void)draw 
{   
    int cellSize = self.bounds.size.width / WIDTH;
    double xOffset = 0;

    CGRect cellFrame = CGRectMake(0, 0, cellSize, cellSize);
    NSUInteger cellIndex = 0;
    cellFrame.origin.x = xOffset;

    for (int i = 0; i < WIDTH; i++)
    {
        cellFrame.origin.y = 0;
        for (int j = 0; j < HEIGHT; j++, cellIndex++)
        {         
                NSNumber *currentCell = [self.levelState.board objectAtIndex:cellIndex];                 
                if (currentCell.intValue == sprouts)
                {
                    [image1 drawInRect:cellFrame];
                }
                else if (currentCell.intValue == grass)
                {
                    [image2 drawInRect:cellFrame];
                }       
            cellFrame.origin.y += cellSize;
        }
        cellFrame.origin.x += cellSize;
    }
}

Answer 1

我解决了它，就像sethHB建议的那样：这个解决方案非常快，足以满足我上面建议的图像数量。

- (void)draw 
{
    CGSize size = self.view.frame.size;
    UIGraphicsBeginImageContext(size);

    CGRect cellFrame = CGRectMake(0, 0, cellSize, cellSize);

    for (int i = 0; i < WIDTH; i++)
    {
        cellFrame.origin.y = 0;
        for (int j = 0; j < HEIGHT; j++, cellIndex++)
        {
                CGPoint pp = CGPointMake(i, j);
                if (currentCell.intValue == sprouts)
                {
                    [image1 drawAtPoint:pp blendMode:kCGBlendModeOverlay alpha:1.0];                 
                }
                else if (currentCell.intValue == grass)
                {
                    [image2 drawAtPoint:pp blendMode:kCGBlendModeOverlay alpha:1.0];                    
                } 
            }
            cellFrame.origin.y += cellSize;
        }
        cellFrame.origin.x += cellSize;
    }
    UIImage* blendedImage = UIGraphicsGetImageFromCurrentImageContext();
    _frontLayer.contents = (id) blendedImage.CGImage;
    UIGraphicsEndImageContext();
}

谢谢SethHB！

如何在CALayer中整理图像的“图像”？

1 个答案: