About IOS quartz2d

quartz2d Introduction (subsequent applications will be relevant)

The first part draws a line

code example:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
    
     / / Start drawing
     / / Set the start of the line
     CGContextMoveToPoint(cxContext, 0, 20);
     / / Set the line midpoint
     CGContextAddLineToPoint(cxContext, 100, 20);
     // render
     CGContextStrokePath(cxContext);
}

We only used four lines of code to draw a line in the view, but it would feel very dull, knowledge of a black straight line.

So we'll give him some attributes.

In order to test, I only added color to him first.

Example code:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
    
     / / Start drawing
     / / Set the start of the line
     CGContextMoveToPoint(cxContext, 0, 20);
     / / Set the line midpoint
     CGContextAddLineToPoint(cxContext, 100, 20);
     / / Set the color
     CGContextSetRGBStrokeColor(cxContext, 1, 0, 0, 1);
     // render
     CGContextStrokePath(cxContext);
}

Can see him turn red.

To analyze the code I've added, I can guess the width and so on.

I'm adding the width below.

Example code:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
    
     / / Start drawing
     / / Set the start of the line
     CGContextMoveToPoint(cxContext, 0, 20);
     / / Set the line midpoint
     CGContextAddLineToPoint(cxContext, 100, 20);
     / / Set the color
     CGContextSetRGBStrokeColor(cxContext, 1, 0, 0, 1);
     / / Set the width
     CGContextSetLineWidth(cxContext, 10);
     // render
     CGContextStrokePath(cxContext);
} 

It's easy to draw a straight line here, but it's not hard to imagine if we're spending more than one test, if we now spend two lines without intersections (we can continue adding lines through Cgcontextaddlinetopoint).

Here's the path, we can draw lines and differentiate them.

Example code:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
     / / Create 2 paths
     CGMutablePathRef path1 = CGPathCreateMutable();
     CGMutablePathRef path2 = CGPathCreateMutable();
     / / Start drawing
     / / draw the first line
     CGPathMoveToPoint(path1, NULL, 0, 20);
     CGPathAddLineToPoint(path1, NULL, 100, 20);
     / / draw a second line
     CGPathMoveToPoint(path2, NULL, 0, 50);
     CGPathAddLineToPoint(path2, NULL, 100, 50);
     / / Add the path to the context
     CGContextAddPath(cxContext, path1);
     CGContextAddPath(cxContext, path2);
     // render
     CGContextStrokePath(cxContext);
     //release because it is CG, so you need to manually release
     CGPathRelease(path1);
     CGPathRelease(path2);
}

Part IIDraw a graphic

Example code:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
     / / draw a rectangle
     CGContextAddRect(cxContext, CGRectMake(20, 20, 100, 100));
     // render
     CGContextStrokePath(cxContext);
    
}

Example code:

- (void)drawRect:(CGRect)rect{
    
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
     / / draw a circle
     CGContextAddArc(cxContext, 100, 100, 25, 0, M_PI, 0);
     // render
     CGContextStrokePath(cxContext);
    
}

Part IIIDraw text

Example code:

- (void)drawRect:(CGRect)rect{
     / / Get the graphics context
     CGContextRef cxContext = UIGraphicsGetCurrentContext();
     / / draw a rectangle
     CGContextAddRect(cxContext, CGRectMake(20, 20, 100, 100));
     // render
     CGContextStrokePath(cxContext);
     //Text content
     NSString *str = @"Xu Bao loves to eat fish Xu Bao love to eat fish Xu Bao love to eat fish Xu Bao love to eat fish Xu Bao love to eat fish";
     / / draw the text to the specified area, automatically wrap the line does not display after the range is drawn
     [str drawInRect:CGRectMake(20, 20, 100, 100) withAttributes:nil];
     / / draw the text to the specified point
// [str drawAtPoint:CGPointMake(0, 0) withAttributes:nil];
    
}

Fourth PartDrawing pictures

Instance code:

- (void)drawRect:(CGRect)rect{
    
     UIImage * image = [UIImage imageNamed:@"2.jpg"];
    
     //tiling
     [image drawAsPatternInRect:self.bounds];
    
}

Example code:

- (void)drawRect:(CGRect)rect{
    
     UIImage * image = [UIImage imageNamed:@"2.jpg"];
    
     //Stretch
     [image drawInRect:self.bounds];
    
}

Instance code:

- (void)drawRect:(CGRect)rect{
    
     UIImage * image = [UIImage imageNamed:@"2.jpg"];
    
     / / The original map specified position (the top left point of the picture)
     [image drawAtPoint:self.center];
    
} 

About IOS quartz2d