使用Cglayer绘图进行撤消和重做

我正在使用绘图应用程序，正在使用CGlayers进行绘图。触摸结束时，我将图像从图层中取出并存储在Array中，以用于撤消操作。

我的触摸结束功能

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{    
    NSLog(@"Touches ended");

    UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextDrawLayerInRect(context, self.bounds, self.drawingLayer);
    m_curImage = UIGraphicsGetImageFromCurrentImageContext();  
    UIGraphicsEndImageContext(); 

    [m_undoArray addObject: m_curImage];
}

我的绘图视图根据用户需求动态扩展，因此假设用户可以绘制一条具有drawView尺寸200 * 200的线，然后将其扩展到200 * 300并再画一条线，然后将其扩展到200 * 300并再画一条线。

这是应用程序的图像

所以现在我在UndoArray中有3张不同大小的图像。

每当我增加/减小画布大小时。我已经写了这段代码

在增加和减少drawingView时，我正在编写此函数

 (void)increaseDecreaseDrawingView 
{ 
self.currentDrawingLayer = nil; 

if(self.permanentDrawingLayer) 
{ 
rectSize = self.bounds; 
NSLog(@"Size%@", NSStringFromCGRect(self.bounds)); 
CGContextRef context = UIGraphicsGetCurrentContext(); 

//self.newDrawingLayer = CGLayerCreateWithContext(context, self.bounds.size, NULL); 
CGFloat scale = self.contentScaleFactor; 
CGRect bounds = CGRectMake(0, 0, self.bounds.size.width * scale, self.bounds.size.height * scale); 
CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL); 
CGContextRef layerContext = CGLayerGetContext(layer); 
CGContextScaleCTM(layerContext, scale, scale); 
self.newDrawingLayer = layer; 


CGContextDrawLayerInRect(layerContext, self.bounds, self.permanentDrawingLayer ); 

self.permanentDrawingLayer = nil; 

} 

对于撤消，我已经编写了这段代码

- (void)Undo
{
     //Destroy the layer and create it once again with the image you get from undoArray.
     self.currentDrawingLayer = Nil;

     CGContextRef layerContext1 = CGLayerGetContext(self.permanentDrawingLayer );
     CGContextClearRect(layerContext1, self.bounds);

     CGContextRef context = UIGraphicsGetCurrentContext();

    for(int i =0; i<[m_rectArrayUndo count];i++)
    {
        CGRect rect = [[m_rectArrayUndo objectAtIndex:i]CGRectValue];
        CGLayerRef undoLayer = CGLayerCreateWithContext(context, rect.size, NULL);

        CGContextRef layerContext = CGLayerGetContext(undoLayer );
        CGContextTranslateCTM(layerContext, 0.0, rect.size.height);
        CGContextScaleCTM(layerContext, 1.0, -1.0);

        CGRect imageFrame;

        NSDictionary *lineInfo = [m_undoArray objectAtIndex:i];
        m_curImage = [lineInfo valueForKey:@"IMAGE"];
       imageFrame = CGRectMake(0 ,0,m_curImage.size.width,m_curImage.size.height);
       CGContextDrawImage(layerContext, imageFrame, m_curImage.CGImage);
       CGContextDrawLayerInRect(context, rect, undoLayer );
       CGContextDrawLayerInRect(layerContext1, rect, undoLayer);
    }          
}

在我的drawRect函数中，我编写了这段代码

- (void)drawRect:(CGRect)rect
{    

            CGContextRef context = UIGraphicsGetCurrentContext();//Get a reference to current context(The context to draw)

            if(self.currentDrawingLayer == nil)
            {                
                CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL);                             
                self.currentDrawingLayer = layer;
            }



            if(self.permanentDrawingLayer == nil)
            {
                CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL);
                self.permanentDrawingLayer = layer;
            }


            if(self.newDrawingLayer == nil)
            {
                CGLayerRef layer = CGLayerCreateWithContext(context, bounds.size, NULL);
                self.newDrawingLayer = layer;
            }

            CGPoint mid1 = midPoint(m_previousPoint1, m_previousPoint2);
            CGPoint mid2 = midPoint(m_currentPoint, m_previousPoint1);



            CGContextRef layerContext = CGLayerGetContext(self.currentDrawingLayer);

            CGContextSetLineCap(layerContext, kCGLineCapRound);
            CGContextSetBlendMode(layerContext, kCGBlendModeNormal);
            CGContextSetLineJoin(layerContext, kCGLineJoinRound);
            CGContextSetLineWidth(layerContext, self.lineWidth);
            CGContextSetStrokeColorWithColor(layerContext, self.lineColor.CGColor);
            CGContextSetShouldAntialias(layerContext, YES);
            CGContextSetAllowsAntialiasing(layerContext, YES);
            CGContextSetAlpha(layerContext, self.lineAlpha);
            CGContextSetFlatness(layerContext, 1.0f);
            CGContextBeginPath(layerContext);
            CGContextMoveToPoint(layerContext, mid1.x, mid1.y);//Position the current point
            CGContextAddQuadCurveToPoint(layerContext, m_previousPoint1.x, m_previousPoint1.y, mid2.x, mid2.y);
            CGContextStrokePath(layerContext);//paints(fills) the line along the current path.

            CGContextDrawLayerInRect(context, self.bounds, self.newDrawingLayer);

            CGContextDrawLayerInRect(context,  self.bounds, self.permanentDrawingLayer);
            CGContextDrawLayerInRect(context, self.bounds, self.currentDrawingLayer);

            [super drawRect:rect];
}

我毫不怀疑

这是正确的方法吗？还是他们有更好的方法。

在这里发生的是，我从undo数组获得的图像不符合rect的要求，而是在新图层上的任意随机位置绘制的。

因此，我想知道如何正确绘制它们，以便在特定位置的CGlayer上正确绘制图像。