Quartz 2D编程指南(2) － 图形上下文

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1. CGContextRef myContext = [[NSGraphicsContext currentContext] graphicsPort];

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1. Listing 2-1  Drawing to a window graphics context
2. @implementation MyQuartzView
3. - (id)initWithFrame:(NSRect)frameRect
4. {
5. self = [super initWithFrame:frameRect];
6. return self;
7. }
8. - (void)drawRect:(NSRect)rec
9. {
10. CGContextRef myContext = [[NSGraphicsContext  currentContext] graphicsPort]; //1
11. // ********** Your drawing code here **********       //2
12. CGContextSetRGBFillColor (myContext, 1, 0, 0, 1);     //3
13. CGContextFillRect (myContext, CGRectMake (0, 0, 200, 100 ));   //4
14. CGContextSetRGBFillColor (myContext, 0, 0, 1, .5);     //5
15. CGContextFillRect (myContext, CGRectMake (0, 0, 100, 200));   //6
16. }
17. @end

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1. Listing 2-2  Calling CGPDFContextCreateWithURL to create a PDF graphics context
2. CGContextRef MyPDFContextCreate (const CGRect *inMediaBox, CFStringRef path)
3. {
4. CGContextRef myOutContext = NULL;
5. CFURLRef url;
6. url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, false);
7. if (url != NULL) {
8. myOutContext = CGPDFContextCreateWithURL (url,  inMediaBox,  NULL);
9. CFRelease(url);
10. }
11. return myOutContext;
12. }

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1. Listing 2-3  Calling CGPDFContextCreate to create a PDF graphics context
2. CGContextRef MyPDFContextCreate (const CGRect *inMediaBox, CFStringRef path)
3. {
4. CGContextRef        myOutContext = NULL;
5. CFURLRef            url;
6. CGDataConsumerRef   dataConsumer;
7. url = CFURLCreateWithFileSystemPath (NULL,  path, kCFURLPOSIXPathStyle, false);
8. if (url != NULL)
9. {
10. dataConsumer = CGDataConsumerCreateWithURL (url);
11. if (dataConsumer != NULL)
12. {
13. myOutContext = CGPDFContextCreate (dataConsumer, inMediaBox, NULL);
14. CGDataConsumerRelease (dataConsumer);
15. }
16. CFRelease(url);
17. }
18. return myOutContext;
19. }

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

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1. Listing 2-5  Creating a bitmap graphics context
2. CGContextRef MyCreateBitmapContext (int pixelsWide, int pixelsHigh)
3. {
4. CGContextRef    context = NULL;
5. CGColorSpaceRef colorSpace;
6. void *          bitmapData;
7. int             bitmapByteCount;
8. int             bitmapBytesPerRow;
9. bitmapBytesPerRow   = (pixelsWide * 4);
10. bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);
11. colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
12. bitmapData = calloc( bitmapByteCount );
13. if (bitmapData == NULL)
14. {
15. fprintf (stderr, "Memory not allocated!");
16. return NULL;
17. }
18. context = CGBitmapContextCreate (bitmapData, pixelsWide, pixelsHigh, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
19. if (context== NULL)
20. {
21. free (bitmapData);
22. fprintf (stderr, "Context not created!");
23. return NULL;
24. }
25. CGColorSpaceRelease( colorSpace );
26. return context;
27. }

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