Quartz－2D绘图之图形上下文详解

 1 - (void)drawRect:(CGRect)rect {
 2     
 3     //    1. 获取一个与视图相关联的上下文
 4     CGContextRef context = UIGraphicsGetCurrentContext();
 5     
 6     // 设置颜色
 7     [[UIColor greenColor]setFill];
 8     
 9     // 2. 增加圆形的路径
10     CGContextAddEllipseInRect(context, CGRectMake(50, 50, 200, 200));
11     // 3. 画圆
12     CGContextFillPath(context);
13 
14 }

 1 CGContextRef MyPDFContextCreate (const CGRect *inMediaBox, CFStringRef path)
 2 {
 3     CGContextRef myOutContext = NULL;
 4     CFURLRef url;
 5     url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, false);
 6     if (url != NULL) {
 7         myOutContext = CGPDFContextCreateWithURL (url,  inMediaBox,  NULL);
 8         CFRelease(url);
 9     }
10     return myOutContext;
11 }

 1 CGContextRef MyPDFContextCreate (const CGRect *inMediaBox, CFStringRef path)
 2 {
 3     CGContextRef        myOutContext = NULL;
 4     CFURLRef            url;
 5     CGDataConsumerRef   dataConsumer;
 6     url = CFURLCreateWithFileSystemPath (NULL,  path, kCFURLPOSIXPathStyle, false);
 7     if (url != NULL)
 8     {
 9         dataConsumer = CGDataConsumerCreateWithURL (url);
10         if (dataConsumer != NULL)
11         {
12             myOutContext = CGPDFContextCreate (dataConsumer, inMediaBox, NULL);
13             CGDataConsumerRelease (dataConsumer);
14         }
15         CFRelease(url);
16     }
17     return myOutContext;
18 } 

 1     CGRect mediaBox;
 2     mediaBox = CGRectMake (0, 0, myPageWidth, myPageHeight);
 3     myPDFContext = MyPDFContextCreate (&mediaBox, CFSTR("test.pdf"));
 4     CFStringRef myKeys[1];
 5     CFTypeRef myValues[1];
 6     myKeys[0] = kCGPDFContextMediaBox;
 7     myValues[0] = (CFTypeRef) CFDataCreate(NULL,(const UInt8 *)&mediaBox, sizeof (CGRect));
 8     CFDictionaryRef pageDictionary = CFDictionaryCreate(NULL, (const void **) myKeys,
 9                                                         (const void **) myValues, 1,
10                                                         &kCFTypeDictionaryKeyCallBacks,
11                                                         & kCFTypeDictionaryValueCallBacks);
12     CGPDFContextBeginPage(myPDFContext, &pageDictionary);
13         // ********** 绘制代码 **********
14         CGContextSetRGBFillColor (myPDFContext, 1, 0, 0, 1);
15         CGContextFillRect (myPDFContext, CGRectMake (0, 0, 200, 100 ));
16         CGContextSetRGBFillColor (myPDFContext, 0, 0, 1, .5);
17         CGContextFillRect (myPDFContext, CGRectMake (0, 0, 100, 200 ));
18     CGPDFContextEndPage(myPDFContext);
19     CFRelease(pageDictionary);
20     CFRelease(myValues[0]);
21     CGContextRelease(myPDFContext);

 1 - (void)createPDFFile
 2 {
 3     // 1. 上下文
 4     // 1) 路径
 5     // 2) 大小，指定为空，那么使用612 * 792大小作为pdf文件的页面大小
 6     // 3) dict
 7     UIGraphicsBeginPDFContextToFile(@"/Users/apple/Desktop/demo.pdf", CGRectZero, nil);
 8    
 9     // 2. 写入内容
10     // 在pdf里面是有页面的，一个页面一个页面的写入的
11     // 建立PDF页面
12     // 一个页面最多能够写入两张图片，因此写入6张图片需要三个页面
13     for (NSInteger i = 0; i < 6; i++) {
14         if (i % 2 == 0) {
15             UIGraphicsBeginPDFPageWithInfo(CGRectMake(0, 0, 612, 792), nil);
16         }
17        
18         // 生成UIImage
19         UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"NatGeo%02d.png", i + 1]];
20         // 写入
21         [image drawAtPoint:CGPointMake(0, 400 * (i % 2))];
22     }
23 
24     // 3. 关闭上下文
25     UIGraphicsEndPDFContext();
26 }

 1 CGContextRef MyCreateBitmapContext (int pixelsWide, int pixelsHigh)
 2 {
 3     CGContextRef    context = NULL;
 4     CGColorSpaceRef colorSpace;
 5     void *          bitmapData;
 6     int             bitmapByteCount;
 7     int             bitmapBytesPerRow;
 8     bitmapBytesPerRow   = (pixelsWide * 4);
 9     bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);
10     colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
11     bitmapData = calloc( bitmapByteCount );
12     if (bitmapData == NULL)
13     {
14         fprintf (stderr, "Memory not allocated!");
15         return NULL;
16     }
17     context = CGBitmapContextCreate (bitmapData, pixelsWide, pixelsHigh, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
18     if (context== NULL)
19     {
20         free (bitmapData);
21         fprintf (stderr, "Context not created!");
22         return NULL;
23     }
24     CGColorSpaceRelease( colorSpace );
25     return context;
26 }

 1 CGRect myBoundingBox;
 2     myBoundingBox = CGRectMake (0, 0, myWidth, myHeight);
 3     myBitmapContext = MyCreateBitmapContext (400, 300);
 4     // ********** Your drawing code here ********** 
 5     CGContextSetRGBFillColor (myBitmapContext, 1, 0, 0, 1);
 6     CGContextFillRect (myBitmapContext, CGRectMake (0, 0, 200, 100 ));
 7     CGContextSetRGBFillColor (myBitmapContext, 0, 0, 1, .5);
 8     CGContextFillRect (myBitmapContext, CGRectMake (0, 0, 100, 200 ));
 9     myImage = CGBitmapContextCreateImage (myBitmapContext);
10     CGContextDrawImage(myContext, myBoundingBox, myImage);
11     char *bitmapData = CGBitmapContextGetData(myBitmapContext); 
12     CGContextRelease (myBitmapContext);
13     if (bitmapData) free(bitmapData); 
14     CGImageRelease(myImage);

+ (instancetype)circleImageWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor
{
    // 1.加载原图
    UIImage *oldImage = [UIImage imageNamed:name];
    
    // 2.开启上下文
    CGFloat imageW = oldImage.size.width + 2 * borderWidth;
    CGFloat imageH = oldImage.size.height + 2 * borderWidth;
    CGSize imageSize = CGSizeMake(imageW, imageH);
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);
    
    // 3.取得当前的上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    
    // 4.画边框(大圆)
    [borderColor set];
    CGFloat bigRadius = imageW * 0.5; // 大圆半径
    CGFloat centerX = bigRadius; // 圆心
    CGFloat centerY = bigRadius;
    CGContextAddArc(ctx, centerX, centerY, bigRadius, 0, M_PI * 2, 0);
    CGContextFillPath(ctx); // 画圆
    
    // 5.小圆
    CGFloat smallRadius = bigRadius - borderWidth;
    CGContextAddArc(ctx, centerX, centerY, smallRadius, 0, M_PI * 2, 0);
    // 裁剪(后面画的东西才会受裁剪的影响)
    CGContextClip(ctx);
    
    // 6.画图
    [oldImage drawInRect:CGRectMake(borderWidth, borderWidth, oldImage.size.width, oldImage.size.height)];
    
    // 7.取图
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    // 8.结束上下文
    UIGraphicsEndImageContext();
    
    return newImage;
}