Question

我使用以下代码绘制图像。所有的触摸代表都在工作，但绘图不会在UIImage上呈现。这是代码。我无法确定问题所在。提前谢谢。

- (id)initWithCoder:(NSCoder *)aDecoder {

    if ((self = [super initWithCoder:aDecoder])) {
        [self setupVariables];
    }

    return self;
}

- (void)drawPic:(UIImage *)thisPic {    
    myPic = thisPic;

    [myPic retain];
    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect {

    float newHeight;
    float newWidth;
    float xPos;
    float yPos;
    float ratio;

    if (myPic != NULL) {
        ratio = myPic.size.height/460;

        if (myPic.size.width/320 > ratio) {
            ratio = myPic.size.width/320;
        }

        newHeight = myPic.size.height/ratio;
        newWidth = myPic.size.width/ratio;

        xPos = (320 - newWidth) / 2;
        yPos = (460 - newHeight) / 2;

        [myPic drawInRect:CGRectMake(xPos, yPos, newWidth, newHeight)];
    }
}

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

    NSArray *allTouches = [[event allTouches] allObjects];

    if ([allTouches count] > 1) {
        return;
    }
    else {
        [self drawPoint:[allTouches objectAtIndex:0]];
    }    
}

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

    NSArray *allTouches = [[event allTouches] allObjects];

    if ([allTouches count] > 1) {
        return;
    }
    else {
        [self drawPoint:[allTouches objectAtIndex:0]];

        self.previousPoint = nil;
        self.point = nil;
    }    
}

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

    NSArray *allTouches = [[event allTouches] allObjects];

    if ([allTouches count] > 1) {
        return;
    }
    else {
        [self drawPoint:[allTouches objectAtIndex:0]];

        self.previousPoint = nil;
        self.point = nil;
    }        
}

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

    NSArray *allTouches = [[event allTouches] allObjects];

    if ([allTouches count] > 1) {
        return;
    }
    else {
        [self drawPoint:[allTouches objectAtIndex:0]];
    }    
}


- (void)dealloc {

    CGContextRelease(offScreenBuffer);
    [point release];
    [previousPoint release];
    [super dealloc];
}

- (void)setupVariables {

    self.point = nil;
    self.previousPoint = nil;
    offScreenBuffer = [self setupBuffer];
}

- (CGContextRef)setupBuffer {

    CGSize size = self.bounds.size;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context =  CGBitmapContextCreate(NULL,size.width,size.height,8,size.width*4, colorSpace,kCGImageAlphaPremultipliedLast);

    CGColorSpaceRelease(colorSpace);

    CGContextTranslateCTM(context, 0, size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    return context;    
}

- (void)drawToBuffer {

    //                  Red  Gr   Blu  Alpha
    CGFloat color[4] = {0.0, 1.0, 0.0, 1.0};

    if (self.previousPoint != nil) {
        CGContextSetRGBStrokeColor(offScreenBuffer, color[0], color[1], color[2], color[3]);

        CGContextBeginPath(offScreenBuffer);
        CGContextSetLineWidth(offScreenBuffer, 10.0);
        CGContextSetLineCap(offScreenBuffer, kCGLineCapRound);

        CGContextMoveToPoint(offScreenBuffer, previousPoint.location.x, previousPoint.location.y);
        CGContextAddLineToPoint(offScreenBuffer, point.location.x, point.location.y);

        CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeColor);

        CGContextDrawPath(offScreenBuffer, kCGPathStroke);
    }    
}

- (void)drawPoint:(UITouch *)touch {

    PointLocation *currentLoc = [[PointLocation alloc] init];

    currentLoc.location = [touch locationInView:self];

    self.previousPoint = self.point;

    self.point = currentLoc;
    [self drawToBuffer];

    [self setNeedsDisplay];

    [currentLoc release];
}

Answer 1

这很简单。您需要在drawRect:中完成所有绘图，而您只是在drawRect:中绘制图像，这就是您只能看到图像的原因。

Answer 2

-(void)drawPic:(UIImage *)thisPic {
//code for UIViewContentModeScaleAspectFit if needed
self.backgroundColor = [UIColor colorWithPatternImage:thisPic];
[self setNeedsDisplay];
}

不在 drawRect 中使用此方法：

[myPic drawInRect：CGRectMake（xPos，yPos，newWidth，newHeight）];

修改

- (void)drawRect:(CGRect)rect { if (!myDrawing) { // CGFloat scale = 0.5; // CATransform3D transform = CATransform3DMakeScale(scale, scale, scale); // [self layer].transform = transform; myDrawing = [[NSMutableArray alloc] initWithCapacity:0]; self.lineOnOffArray = [[NSMutableArray alloc] initWithCapacity:0]; //arrPenThickness = [[NSMutableArray alloc] initWithCapacity:0]; } CGContextRef ctx = UIGraphicsGetCurrentContext(); if ([myDrawing count] > 0) { for (int i = 0 ; i < [myDrawing count] ; i++) { NSArray *thisArray = [myDrawing objectAtIndex:i]; NSString *onOffFlag = [self.lineOnOffArray objectAtIndex:i]; if (([thisArray count] > 2) && (onOffFlag == @"1")){ float penT = [[arrPenThickness objectAtIndex:i] floatValue]; NSString* penC = [arrPenColors objectAtIndex:i]; NSArray *arr = [penC componentsSeparatedByString:@","]; float r = [[arr objectAtIndex:0]floatValue]; float g = [[arr objectAtIndex:1]floatValue]; float b = [[arr objectAtIndex:2]floatValue]; float a = [[arr objectAtIndex:3]floatValue]; CGContextSetRGBStrokeColor(ctx, r/255.0, g/255.0, b/255.0, a); CGContextSetLineCap(ctx, kCGLineCapRound); CGContextSetLineWidth(ctx, penT); float thisX = [[thisArray objectAtIndex:0] floatValue]; float thisY = [[thisArray objectAtIndex:1] floatValue]; CGContextBeginPath(ctx); for (int j = 2; j < [thisArray count] ; j+=2) { CGContextMoveToPoint(ctx, thisX, thisY); thisX = [[thisArray objectAtIndex:j] floatValue]; thisY = [[thisArray objectAtIndex:j+1] floatValue]; CGContextAddLineToPoint(ctx, thisX,thisY); } CGContextStrokePath(ctx); } } } }

在UIImage上绘图的问题

2 个答案: