ios - 在 iOS 中绘制沿路径均匀分布的图像

Question

我想做的是在屏幕上移动手指 (touchesMoved) 并沿着 touchesMoved 生成的点绘制间隔均匀的图像(可能是 CGImageRefs)。我可以画线，但我想要生成的东西看起来像这样(对于这个例子，我使用的是箭头图像，但它可以是任何图像，可以是我的狗的照片 :))主要是以在 iPhone 或 iPad 上用手指绘图时使图像间隔均匀。

Answer 1

首先，Kendall 获得了巨大的支持。因此，根据他的回答，这里是获取 UIImage 的代码，根据触摸之间的距离沿着路径(不是真正的 pathRef，只是由点创建的逻辑路径)在屏幕上绘制它，然后旋转图像正确地基于当前点和先前点的 VECTOR。我希望你喜欢它:

首先你需要加载一个图像来一遍又一遍地用作CGImage:

NSString *imagePath = [[NSBundle mainBundle] pathForResource:@"arrow.png" ofType:nil];
  UIImage *img = [UIImage imageWithContentsOfFile:imagePath];
  image = CGImageRetain(img.CGImage);

确保在你调用的 dealloc 中

 CGImageRelease(image);

然后在 touchesBegan 中，只需将起始点存储在方法外部范围内的 var 中(像这样在标题中声明它:) 在这种情况下，我将绘制到 UIView 中

@interface myView : UIView {
    CGPoint lastPoint;
    }
@end

然后开始接触:

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

{

UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self];

最后在 touchesMoved 中，将位图绘制到屏幕上，然后当你的距离移动足够多时(在我的例子中是 73，因为我的图像是 73 像素 x 73 像素)将该图像绘制到屏幕上，保存新图像并设置 lastPoint 等于 currentPoint

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

        UITouch *touch = [touches anyObject];   
        currentPoint = [touch locationInView:self];

        double deltaX = lastPoint.x - currentPoint.x;
        double deltaY = lastPoint.y - currentPoint.y;

        double powX = pow(deltaX,2);
        double powY = pow(deltaY,2);

        double distance = sqrt(powX + powY);
        if (distance >= 73){

            lastPoint = currentPoint;

             UIGraphicsBeginImageContext(self.frame.size);
            [drawImage.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
            CGContextSaveGState(UIGraphicsGetCurrentContext());

            float angle = atan2(deltaX, deltaY);
            angle *= (M_PI / 180);


            CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(currentPoint.x, currentPoint.y, 73, 73),[self CGImageRotatedByAngle:image angle:angle * -1]);
            CGContextRestoreGState(UIGraphicsGetCurrentContext());
             drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            distance = 0;

        }

    }


    - (CGImageRef)CGImageRotatedByAngle:(CGImageRef)imgRef angle:(CGFloat)angle
{
    CGFloat angleInRadians = angle * (M_PI / 180);
    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);

    CGRect imgRect = CGRectMake(0, 0, width, height);
    CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
    CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, transform);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef bmContext = CGBitmapContextCreate(NULL,
                                                   rotatedRect.size.width,
                                                   rotatedRect.size.height,
                                                   8,
                                                   0,
                                                   colorSpace,
                                                   kCGImageAlphaPremultipliedFirst);
    CGContextSetAllowsAntialiasing(bmContext, FALSE);
    CGContextSetInterpolationQuality(bmContext, kCGInterpolationNone);
    CGColorSpaceRelease(colorSpace);
    CGContextTranslateCTM(bmContext,
                          +(rotatedRect.size.width/2),
                          +(rotatedRect.size.height/2));
    CGContextRotateCTM(bmContext, angleInRadians);
    CGContextTranslateCTM(bmContext,
                          -(rotatedRect.size.width/2),
                          -(rotatedRect.size.height/2));
    CGContextDrawImage(bmContext, CGRectMake(0, 0,
                                             rotatedRect.size.width,
                                             rotatedRect.size.height),
                       imgRef);

    CGImageRef rotatedImage = CGBitmapContextCreateImage(bmContext);
    CFRelease(bmContext);
    [(id)rotatedImage autorelease];

    return rotatedImage;
}

这将创建一个看起来像这样的图像:

将添加以下内容(对上述代码进行一些更改，以尝试填充快速移动时 touchesMoved 缺少一些点的空白:

CGPoint point1 = CGPointMake(100, 200);

CGPoint point2 = CGPointMake(300, 100);



double deltaX = point2.x - point1.x;
double deltaY = point2.y - point1.y;

double powX = pow(deltaX,2);
double powY = pow(deltaY,2);

double distance = sqrt(powX + powY);

distance = 0;


for (int j = 1; j * 73 < distance; j++ )
{
    double x =  (point1.x + ((deltaX / distance) * 73 * j));
    double y =  (point1.y + ((deltaY / distance) * 73 * j));


    NSLog(@"My new point is x: %f y :%f", x, y);
}