iOS Development - Quartz2D Supplement

Today, I will give students a comprehensive explanation of Quartz2D and related practical examples of Quartz2D: For examples, please refer to the blog post about the Quartz2D project I posted before on CSDN, so I won't talk nonsense, just go to the code~

http://blog.csdn.net/ZZ_IOSdeveloper
- Quartz2D drawing method name
- Drawing writing of NSString string
- Using Quartz2D to zoom in and out of pictures (low efficiency)
- Using Quartz2D to draw pictures
- Using Quartz2D to achieve gradual change Color Filling Method
- Quartz2D Usage Notes ( 重点)
- Quartz2D Function Description ( 方法解读)
- Use Quartz2D to draw dynamic curves

Quartz2D drawing method name

CGContextRef context = UIGraphicsGetCurrentContext(); 设置上下文
CGContextMoveToPoint 开始画线
CGContextAddLineToPoint 画直线
CGContextAddEllipseInRect 画一椭圆
CGContextSetLineCap 设置线条终点形状
CGContextSetLineDash 画虚线
CGContextAddRect 画一方框
CGContextStrokeRect 指定矩形
CGContextStrokeRectWithWidth 指定矩形线宽度
CGContextStrokeLineSegments 一些直线
CGContextAddArc 画已曲线 前俩店为中心 中间俩店为起始弧度 最后一数据为0则顺时针画 1则逆时针
CGContextAddArcToPoint(context,0,0, 2, 9, 40);//先画俩条线从point 到 弟1点 ， 从弟1点到弟2点的线 切割里面的圆
CGContextSetShadowWithColor 设置阴影
CGContextSetRGBFillColor 这只填充颜色
CGContextSetRGBStrokeColor 画笔颜色设置
CGContextSetFillColorSpace 颜色空间填充
CGConextSetStrokeColorSpace 颜色空间画笔设置
CGContextFillRect 补充当前填充颜色的rect
CGContextSetAlaha 透明度
CGContextTranslateCTM 改变画布位置
CGContextSetLineWidth 设置线的宽度
CGContextAddRects 画多个线
CGContextAddQuadCurveToPoint 画曲线
CGContextStrokePath 开始绘制图片
CGContextDrawPath 设置绘制模式
CGContextClosePath 封闭当前线路
CGContextTranslateCTM(context, 0, rect.size.height); CGContextScaleCTM(context, 1.0, -1.0);反转画布
CGContextSetInterpolationQuality 背景内置颜色质量等级
CGImageCreateWithImageInRect 从原图片中取小图
CGColorGetComponents（）返回颜色的各个直 以及透明度 可用只读const float 来接收 是个数组

Drawing write of NSString string

• The drawing method of NSString itself

// 通过如下方法实现即可
- (CGSize)drawInRect:(CGRect)rect withFont:(UIFont *)font lineBreakMode:(UILineBreakMode)lineBreakMode alignment:(UITextAlignment)alignment;

Use Quartz2D to zoom in and out of pictures ( 效率低了点)

UIGraphicsBeginImageContext(newSize);
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Drawing pictures with Quartz2D

CGImageRef image＝CGImageRetain(img.CGImage);
CGContextDrawImage(context, CGRectMake(10.0, height -
100.0, 90.0, 90.0), image);

Using Quartz2D to realize the method of changing color filling

CGContextClip(context);
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
CGFloat colors[] = {
204.0 / 255.0, 224.0 / 255.0, 244.0 / 255.0, 1.00,
29.0 / 255.0, 156.0 / 255.0, 215.0 / 255.0, 1.00,
0.0 / 255.0, 50.0 / 255.0, 126.0 / 255.0, 1.00,
};
CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));
CGColorSpaceRelease(rgb);
CGContextDrawLinearGradient(context, gradient,CGPointMake (0.0,0.0) ,CGPointMake(0.0,self.frame.size.height),
kCGGradientDrawsBeforeStartLocation);

Note on Quartz2D usage ( 注意点)

• Note: After drawing the picture, you must
• First use CGContextStrokePath to draw the line, that is, the shape
• Then use CGContextFillPath to fill the color inside the shape.
• When filling a path, the sub-paths in the path are filled independently.
• In the case of overlapping paths, there are two rules for determining whether a point is filled or not:
• 1> nonzero winding number rule: nonzero winding number rule, if a point is crossed from left to right, counter +1, crossed from right to left, counter -1, and finally, if the result is 0, then do not fill, If it is non-zero, then fill.
• 2> even-odd rule: Even-odd rule, if a point is crossed, then +1, and finally an odd number, then it will be filled, even numbers will not be filled, and it has nothing to do with the direction.

Quartz2D Function Description (方法解读)

CGContextEOFillPath 使用奇偶规则填充当前路径
CGContextFillPath 使用非零绕数规则填充当前路径
CGContextFillRect 填充指定的矩形
CGContextFillRects 填充指定的一些矩形
CGContextFillEllipseInRect 填充指定矩形中的椭圆
CGContextDrawPath 两个参数决定填充规则
kCGPathFill 表示用非零绕数规则
kCGPathEOFill 表示用奇偶规则
kCGPathFillStroke 表示填充
kCGPathEOFillStroke 表示描线，不是填充

设置当一个颜色覆盖上另外一个颜色，两个颜色怎么混合默认方式是:
result = (alpha * foreground) + (1 - alpha) * background
CGContextSetBlendMode :设置blend mode.
CGContextSaveGState :保存blend mode.
CGContextRestoreGState:在没有保存之前，用这个函数还原blend mode.
CGContextSetBlendMode 混合俩种颜色

Drawing dynamic curves with Quartz2D

• Three class implementations
• UIBezierPath ,CAShapeLayer ,CABasicAnimation
  

UIBezierPath实现绘画相应的曲线路径，CAShapeLayer 为path 提供展示的位置，并将CABasicAnimation 所创建的动画加入到Path上。
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(0.0,20.0)];
[path addLineToPoint:CGPointMake(120.0, 500.0)];
[path addLineToPoint:CGPointMake(220, 0)];
[path addLineToPoint:CGPointMake(310, 40)];
[path addLineToPoint:CGPointMake(SCREEN_WIDTH, 110)];

然后我们再为CAShapeLayer创建自己的属性，并且将我们的path赋值给它。如果没有这个赋值的话，这个layer就不能为我们画出这个效果了，并且也是一个不完整的layer.
CAShapeLayer *pathLayer = [CAShapeLayer layer];
pathLayer.frame = self.view.bounds;
pathLayer.path = path.CGPath;
pathLayer.strokeColor = [[UIColor redColor] CGColor];
pathLayer.fillColor = nil;
pathLayer.lineWidth = 2.0f;
pathLayer.lineJoin = kCALineJoinBevel;
[self.view.layer addSublayer:pathLayer];

最后，我们将动画赋值给我们的layer.我们的动画效果中，可以改变其中的一些参数来控制它的绘画效果。
CABasicAnimation *pathAnimation = [CABasicAnimationanimationWithKeyPath:@"strokeEnd"];
pathAnimation = [CABasicAnimationanimationWithKeyPath:@"strokeEnd"];
pathAnimation.duration = 2.0;
pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];
[pathLayer addAnimation:pathAnimation forKey:@"strokeEnd"];