Question

我正在制作一个绘制应用程序，我所做的是从前一个视图控制器中的相机胶卷加载图像，然后将其发送到此处，并将其加载到mainImage中，然后应用程序在照片。现在，如果我选择橡皮擦工具，我可以擦除应用程序绘制的内容，但它仅在我第一次擦除时起作用，因为当我释放第一次触摸并再次尝试擦除时它什么也没做。即使我选择另一个按钮来绘制其他线条，然后再次选择橡皮擦，它也不会擦除。任何人都可以帮我这个吗？

@synthesize mainImage;
@synthesize tempDrawImage;

- (void)viewDidLoad
{
    red = 255.0/255.0;
    green = 0/255.0;
    blue = 255.0/255.0;
    brush = 10.0;
    opacity = 1.0;
    self.mainImage.image = [camViewController image]; //load photo from camera roll from previous view controller
    [super viewDidLoad];

    //draw line in the middle of the screen
    [self drawMiddleRectangleBrushSize:20];

}

-(void)drawMiddleRectangleBrushSize:(float)brushSize{
    UIGraphicsBeginImageContext(self.view.frame.size);
    [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), self.view.frame.size.width/2, 0);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), self.view.frame.size.width/2, self.view.frame.size.height);
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSize );
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);

    CGContextStrokePath(UIGraphicsGetCurrentContext());
    self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    [self.tempDrawImage setAlpha:opacity];
    UIGraphicsEndImageContext();
}

- (IBAction)pencilPressed:(id)sender {

    UIButton * PressedButton = (UIButton*)sender;
    _eraserPress = NO;
    switch(PressedButton.tag)
    {
        case 0:
            red = 0.0/255.0;
            green = 0.0/255.0;
            blue = 0.0/255.0;
            break;
        case 1:
            red = 105.0/255.0;
            green = 105.0/255.0;
            blue = 105.0/255.0;
            break;
        case 2:
            red = 255.0/255.0;
            green = 0.0/255.0;
            blue = 0.0/255.0;
            break;
        case 3:
            red = 0.0/255.0;
            green = 0.0/255.0;
            blue = 255.0/255.0;
            break;
        case 4:
            red = 102.0/255.0;
            green = 204.0/255.0;
            blue = 0.0/255.0;
            break;
        case 5:
            red = 102.0/255.0;
            green = 255.0/255.0;
            blue = 0.0/255.0;
            break;
        case 6:
            red = 51.0/255.0;
            green = 204.0/255.0;
            blue = 255.0/255.0;
            break;
        case 7:
            red = 160.0/255.0;
            green = 82.0/255.0;
            blue = 45.0/255.0;
            break;
        case 8:
            red = 255.0/255.0;
            green = 102.0/255.0;
            blue = 0.0/255.0;
            break;
        case 9:
            red = 255.0/255.0;
            green = 255.0/255.0;
            blue = 0.0/255.0;
            break;
    }
}

- (IBAction)eraserPressed:(id)sender {

    red = 255.0/255.0;
    green = 255.0/255.0;
    blue = 255.0/255.0;
    opacity = 1.0;
    _eraserPress = YES;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    mouseSwiped = NO;
    UITouch *touch = [touches anyObject];
    lastPoint = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    mouseSwiped = YES;
    UITouch *touch = [touches anyObject];
    CGPoint currentPoint = [touch locationInView:self.view];

    if(_eraserPress == NO){

    UIGraphicsBeginImageContext(self.view.frame.size);
    [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);

    CGContextStrokePath(UIGraphicsGetCurrentContext());
    self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    [self.tempDrawImage setAlpha:opacity];
    UIGraphicsEndImageContext();

    lastPoint = currentPoint;
    }
    if(_eraserPress == YES){
        UIGraphicsBeginImageContext(self.view.frame.size);
        [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];

        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(),brush);
        CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);

        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), YES);
        CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES);
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        CGContextSetFlatness(UIGraphicsGetCurrentContext(), 0.1f);
        self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    if(!mouseSwiped) {
        UIGraphicsBeginImageContext(self.view.frame.size);
        [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity);
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        CGContextFlush(UIGraphicsGetCurrentContext());
        self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }

    UIGraphicsBeginImageContext(self.mainImage.frame.size);
    [self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
    [self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
    self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
    self.tempDrawImage.image = nil;
    UIGraphicsEndImageContext();
}

Answer 1

当您处于＆＃34;删除模式＆＃34;时，在touchesMoved方法中，您没有更新lastPoint。这可能是造成问题的原因。

Answer 2

我已经完成了对合并这两个图像的这两行代码的评论，当两个图像合并为一个图像时，您就不能再擦除了。希望它有所帮助，欢呼！

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    if(!mouseSwiped) {
    //code...
    }
    //self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
    //self.tempDrawImage.image = nil;
}

使用石英2d绘图应用程序不能多次擦除绘制的线条

2 个答案: