绘制图形-移动,旋转,阴影,渐变

// Only override drawRect: if you perform custom drawing.

// An empty implementation adversely affects performance during animation.

- (void)drawRect:(CGRect)rect {

    UIBezierPath *path = [UIBezierPath bezierPath];

    //绘图的起点坐标

    [path moveToPoint:CGPointMake(50, 50)];

    //依次连接各个坐标

    [path addLineToPoint:CGPointMake(50, 100)];

    [path addLineToPoint:CGPointMake(100, 100)];

    [path addLineToPoint:CGPointMake(100, 50)];

    //闭合

    [path closePath];

    //上下文

    CGContextRef context = UIGraphicsGetCurrentContext();

    //保存上下文状态

    CGContextSaveGState(context);

    //绘制图形轮廓

    [path stroke];

    //移动原点，使各个坐标依次移动

    CGContextTranslateCTM(context, 50, 50);

    //设置颜色

    UIColor *fillColor = [UIColor greenColor];

    //填充颜色

    [fillColor setFill];

    //填充

    [path fill];

    //再次移动原点坐标

    CGContextTranslateCTM(context, 50, 50);

    //图形旋转

    CGContextRotateCTM(context, 3.14/4);

    fillColor = [UIColor orangeColor];

    [path fill];

    //[path stroke];

    //恢复上下文状态,

    CGContextRestoreGState(context);

    

    CGContextSaveGState(context);

    CGContextTranslateCTM(context, 50, 200);

    //图形阴影

    CGContextSetShadow(context, CGSizeMake(10, 10), 7);

    fillColor = [UIColor grayColor];

    [fillColor setFill];

    [path fill];

    CGContextRestoreGState(context);//恢复上下文状态

    

    CGContextSaveGState(context);//保存上下文状态

    CGContextTranslateCTM(context, 50, 300);

    

    //定义渐变

    CGGradientRef myGradient;

    //声明色彩空间

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGFloat components[8] = {1.0, 0.0, 0.0, 1.0,

            0.0, 0.0, 1.0, 1.0

    };

    CGFloat locations[2] = {0.2, 0.8};

    int num = 2;

    myGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, num);

    [path addClip];

    CGContextDrawLinearGradient(context, myGradient, CGPointMake(0, 0), CGPointMake(100, 0), 0);

    

    CGColorSpaceRelease(colorSpace);

    CGGradientRelease(myGradient);

    CGContextRestoreGState(context);

   

}