Graphics总结
获得context
UIView的drawRect方法中：
UIGraphicsGetCurrentContext();
创建画布，获得context。最常用的imageContext：
UIGraphicsBeginImageContextWithOptions(annoImage.size, NO, 0.0); CGContextRef context = UIGraphicsGetCurrentContext();
各种绘图
线条颜色、填充颜色、线条宽度、虚线、线条形状等
CGContextStrokePath时候，线条颜色和填充颜色生效。
（两种颜色不能同时生效，所以如果想同时有填充颜色和线条颜色，需要画两次？）
- (UIImage *)drawImage{
UIGraphicsBeginImageContext(CGSizeMake(202, 202));
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1, 1, 1, 0xa0/255.0);//线条颜色
CGContextSetLineWidth(context, 1.0);//线条宽度
CGContextAddRect(context, CGRectMake(0,0, 202, 202));
CGContextStrokePath(context);
CGContextSetFillColorWithColor(context, [UIColor greenColor].CGColor);//填充颜色
CGContextFillRect(context, CGRectMake(0, 0, 15, 2));
CGContextFillRect(context, CGRectMake(0, 0, 2, 15));
CGContextFillRect(context, CGRectMake(202-15, 0, 15, 2));
CGContextFillRect(context, CGRectMake(202-2, 0, 2, 15));
CGContextFillRect(context, CGRectMake(0, 202-2, 15, 2));
CGContextFillRect(context, CGRectMake(0, 202-15, 2, 15));
CGContextFillRect(context, CGRectMake(202-15, 202-2, 15, 2));
CGContextFillRect(context, CGRectMake(202-2, 202-15, 2, 15));
CGContextStrokePath(context);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
CGContextSetLineCap 设置线条终点形状
CGContextSetLineDash 画虚线
画矩形
1.使用系统方法直接画矩形：
CGContextAddRect(context, CGRectMake(0,0, 202, 202));//画矩形边框 CGContextFillRect(context, CGRectMake(0, 0, 15, 2));//画实心矩形
2.画path:
通过CGContextMoveToPoint、CGContextAddLineToPoint绘制。绘制完成后CGContextClosePath，然后使用CGContextStrokePath填充颜色。
画弧线
1.CGContextAddArcToPoint
- (void)getDrawPath:(CGContextRef)context//自定义annotation calloutView的边框
{
CGContextSetStrokeColorWithColor(context, [UIColor lightGrayColor].CGColor);
CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
CGContextSetLineWidth(context, 0.5);
CGRect rrect = self.bounds;
CGFloat radius = 10;
CGFloat minx = CGRectGetMinX(rrect),
midx = CGRectGetMidX(rrect),
maxx = CGRectGetMaxX(rrect);
CGFloat miny = CGRectGetMinY(rrect),
// midy = CGRectGetMidY(rrect),
maxy = CGRectGetMaxY(rrect)-Arror_height;
CGContextMoveToPoint(context, midx+Arror_height, maxy);
CGContextAddLineToPoint(context,midx, maxy+Arror_height);
CGContextAddLineToPoint(context,midx-Arror_height, maxy);
CGContextAddArcToPoint(context, minx, maxy, minx, miny, radius);
CGContextAddArcToPoint(context, minx, miny, maxx, miny, radius);
CGContextAddArcToPoint(context, maxx, miny, maxx, maxx, radius);
CGContextAddArcToPoint(context, maxx, maxy, midx, maxy, radius);
CGContextAddLineToPoint(context, midx+Arror_height, maxy);
CGContextFillPath(context);
CGContextClosePath(context);
CGContextMoveToPoint(context, midx+Arror_height, maxy);
CGContextAddLineToPoint(context,midx, maxy+Arror_height);
CGContextAddLineToPoint(context,midx-Arror_height, maxy);
CGContextAddArcToPoint(context, minx, maxy, minx, miny, radius);
CGContextAddArcToPoint(context, minx, miny, maxx, miny, radius);
CGContextAddArcToPoint(context, maxx, miny, maxx, maxx, radius);
CGContextAddArcToPoint(context, maxx, maxy, midx, maxy, radius);
// CGContextAddLineToPoint(context, midx+Arror_height, maxy);
CGContextClosePath(context);
CGContextStrokePath(context);
}
CGContextAddArcToPoint：当前点到第一个点的线、与第一个点到第二个点的线相交，然后画弧线。当前点与弧线连接，第二个点与弧线不连接，弧线结束即结束。
2.CGContextAddArc
- (UIImageView *)createShadowImageView{//创建渐变颜色的扇形
UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.view.frame.size.height*1.1/2, self.view.frame.size.height*1.1/2), NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGPoint center = CGPointMake(self.view.frame.size.width/2, self.view.frame.size.height/2);
for (int i = 0; i < 90; i++){
CGContextSetRGBFillColor(context, 1, 1, 1, (i/90.0)*0.2);
CGContextMoveToPoint(context, 0, 0);
CGContextAddArc(context, 0, 0, center.y*1.1, i*(M_PI/180), (i+1)*(M_PI/180), 0);
CGContextClosePath(context);
CGContextFillPath(context);
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *imageView = [[UIImageView alloc]initWithImage:image];
return imageView;
}
CGContextAddArc(CGContextRef c, CGFloat x, CGFloat y, CGFloat radius, CGFloat startAngle, CGFloat endAngle, int clockwise)。colckwize为方向。
画椭圆、正圆
CGContextAddEllipseInRect、CGContextFillEllipseInRect
画图片
画VIEW
[imageView.layer renderInContext:context];
[view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
Context的处理
缩小图片并截取成圆形（截取矩形类似操作）
画出形状后，CGContextClip，再画的内容都在形状的范围内才画出了。
- (UIImage *)getSmallImage{
UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 57, 57)];
imageView.image = selectedImage;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(57, 57), NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddEllipseInRect(context, CGRectMake(0, 0, 57, 57));
CGContextClip(context);
[imageView.layer renderInContext:context];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
挖空
CGContextClearRect(context, rect);
挖一个圆形
首先Clip一个圆形，然后ClearRect。
CGContextAddEllipseInRect(context, r);
CGContextClip(context);
CGContextClearRect(context, r);
从context的某个位置开始绘图
- (UIImage*)createImageWithPic:(UIImageView*)pic inImage:(UIImage*)annoImage{//在annotation上添加照片
UIGraphicsBeginImageContextWithOptions(annoImage.size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
[annoImage drawInRect:CGRectMake(0, 0, annoImage.size.width, annoImage.size.height)];
CGContextTranslateCTM(context, 4.1, 1.6);
[pic.layer renderInContext:context];
CGContextTranslateCTM(context, -4.1, -1.6);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
CGContextTranslateCTM(context, 4.1, 1.6)，修改原点，则绘图的起始位置为{4.1,1.6}。绘制完成后调用CGContextTranslateCTM(context, -4.1, -1.6)。
截取图片，返回截取到的图片
- (void)setBackground{
UIImage *image = [UIImage imageNamed:@"image_health_bkg.png"];
UIImageView *imageView = [[UIImageView alloc]initWithImage:image];
imageView.frame = [UIScreen mainScreen].bounds;
UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, -64);
[imageView.layer renderInContext:context];
// CGContextTranslateCTM(context, 0, 64);
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.layer.contents = (id)image.CGImage;
return;
}
图片比VIEW大，要把上边儿部分截去64。建立一个VIEW大小的context，CGContextTranslateCTM(context, 0, -64)让绘图原点从{0,-64}开始，再画图就可以了。
imagePicker获取最终截取的图片
UIScrollView *scrollView = (UIScrollView *)[self findView:testViewController.view withName:@"PLImageScrollView"];
UIView *imageView = [self findView:testViewController.view withName:@"PLExpandableImageView"];
CGPoint contentOffset = scrollView.contentOffset;
double scale = imageView.transform.a;
double x = imageView.frame.origin.x;
double y = imageView.frame.origin.y;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.view.frame.size.width/scale, self.view.frame.size.width/scale), NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, -(contentOffset.x - x)/scale, -(contentOffset.y+124-y)/scale);
[originalimage drawInRect:CGRectMake(0, 0, originalimage.size.width, originalimage.size.height)];
CGContextTranslateCTM(context, (contentOffset.x- x)/scale, (contentOffset.y+124-y)/scale);
selectedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
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