如何将 CGContext 保存到 NSUndoManager答案

【问题标题】：How would I save a CGContext into an NSUndoManager如何将 CGContext 保存到 NSUndoManager
【发布时间】：2009-12-21 03:56:58
【问题描述】：

我希望能够使用这些方法将CGContext 保存到我的NSUndoManager 中

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{
    UITouch *touch = [touches anyObject];
    CGPoint currentPoint = [touch locationInView:self.view];
             currentPoint.x = currentPoint.x;
             currentPoint.y = currentPoint.y;
             mouseSwiped = YES;
             UIGraphicsBeginImageContext(self.view.frame.size);
             [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
             CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), YES);
             CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
             CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSizeVal);
             CGContextSetAlpha(UIGraphicsGetCurrentContext(), drawingColorAlpha);
             CGContextSaveGState(UIGraphicsGetCurrentContext());    //Probably right here
             CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 
                                        drawingColorRed,
                                        drawingColorGreen,
                                        drawingColorBlue,
                                        drawingColorAlpha);
             CGContextBeginPath(UIGraphicsGetCurrentContext());
             CGContextMoveToPoint(UIGraphicsGetCurrentContext(),
                                  lastPoint.x,
                                  lastPoint.y);
             CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), 
                                     currentPoint.x,
                                     currentPoint.y);
             CGContextStrokePath(UIGraphicsGetCurrentContext());
             drawImage.image = UIGraphicsGetImageFromCurrentImageContext();    //drawImage is the UIImageView that I am drawing my context to
              NSLog(@"current point x: %d current point y: %d",currentPoint.x, currentPoint.y);    //Used for my purposes
             lastPoint = currentPoint;
             mouseMoved++;

和

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{
    if (!optionsDisplayerVisible && canDraw)
     {
        if(!mouseSwiped)
         {
            UIGraphicsBeginImageContext(self.view.frame.size);
            [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
            CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), YES);
            CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
            CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSizeVal);
            CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 
                                       drawingColorRed,
                                       drawingColorGreen,
                                       drawingColorBlue,
                                       drawingColorAlpha);
            CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
            CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
            CGContextStrokePath(UIGraphicsGetCurrentContext());
            CGContextFlush(UIGraphicsGetCurrentContext());
            drawImage.image = UIGraphicsGetImageFromCurrentImageContext();    //drawImage is the UIImageView that I am drawing to
            UIGraphicsEndImageContext();
         }
     }
}

顺便说一下，如果你想知道我的 NSUndoManager 名为 undoDrawing

【问题讨论】：

标签： iphone uiimageview cgcontext undo-redo

【解决方案1】：

我不相信你想保存CGContext，因为它是堆栈的一部分，当你以后需要它时它是无效的。相反，只需保存图像本身。首先，不要在整个框架上创建上下文。您只需要 currentPoint 和 lastPoint 之间的矩形。然后，在开始绘制之前，从当前上下文中获取图像（UIGraphicsGetImageFromCurrentImageContext ()）并将其与帧一起保存到 NSUndoManager。

如果您不熟悉仅针对脏矩形优化绘图，请从更简单的版本开始，然后在绘制之前将整个图像保存到 undomanager。

【讨论】：