原文地址：http://blog.csdn.net/pjk1129/article/details/7161383


1、绘图总结:

绘图前设置:

  1. CGContextSetRGBFillColor/CGContextSetFillColorWithColor  //填充色    
  2. CGContextSetRGBStrokeColor/CGContextSetStrokeColorWithColor //笔颜色    
  3. CGContextSetLineWidth   //线宽度  

绘图后设置:

注:  画完图后,必须 先用CGContextStrokePath来描线,即形状，后用CGContextFillPath来填充形状内的颜色.

2.常见图形绘制:

  1. CGContextFillRect/CGContextFillRects    
  2. CGContextFillEllipseInRect    
  3. CGContextAddRect/CGContextAddRects    
  4. CGContextAddEllipseInRect    
  5. CGContextAddLines    
  6. CGContextMoveToPoint    
  7. CGContextAddLineToPoint  

3.常见控制方法:

  1. CGContextSaveGState    
  2. CGContextRestoreGState  

4.创建内存图像context:

  1. CGBitmapContextCreate       <-----CGContextRlease释放    
  2. CGColorSpaceCreateWithName    (KCGColorSpaceGenericRGB)    
  3. CGColorSpaceRlease    
  4. CGBitmapContextCreateImage()   <-----CGImageRlease 释放.    
  5. eg:    
  6. CGContextRefMyCreateBitmapContext(intpixelsWide,intpixelsHigh)    
  7. {    
  8. CGContextRef    context=NULL;    
  9. CGColorSpaceRefcolorSpace;    
  10. void*          bitmapData;    
  11. int             bitmapByteCount;    
  12. int             bitmapBytesPerRow;    
  13. bitmapBytesPerRow   =(pixelsWide*4);    
  14. bitmapByteCount     =(bitmapBytesPerRow*pixelsHigh);    
  15. colorSpace=CGColorSpaceCreateDeviceRGB();    
  16. bitmapData=malloc(bitmapByteCount);    
  17. if(bitmapData==NULL)    
  18. {    
  19. fprintf(stderr,"Memorynotallocated!");    
  20. returnNULL;    
  21. }    
  22. context=CGBitmapContextCreate(bitmapData,    
  23.  pixelsWide,    pixelsHigh,    8,     
  24. bitmapBytesPerRow,    colorSpace,    
  25.  kCGImageAlphaPremultipliedLast);    
  26. if(context==NULL)    
  27. {    
  28. free(bitmapData);    
  29. fprintf(stderr,"Contextnotcreated!");    
  30. returnNULL;    
  31. }    
  32. CGColorSpaceRelease(colorSpace);    
  33. returncontext;    
  34. }  

5.图形的变换:

  1. CGContextTranslateCTM    
  2. CGContextRotateCTM    
  3. CGContextScaleCTM  

6.常用函数:

  1.   CGRectContainsPoint();    
  2. CGRectContainsRect();    
  3. CGRectIntersectsRect();    
  4. CGRectIntersection();    
  5. CGPointEqualToPoint();    
  6. CGSizeEqualToSize();  

7.从原图片中取小图.

  1. CGImageCreateWithImageInRect  

8.屏幕快照:

  1. #import "QuartzCore/QuartzCore.h"    

  3. UIGraphicsBeginImageContext(yourView.frame.size);    
  4. [[yourView layer] renderInContext:UIGraphicsGetCurrentContext()];    
  5. UIImage*screenshot =UIGraphicsGetImageFromCurrentImageContext();    
  6. UIGraphicsEndImageContext();    
  7. from:http://www.cppblog.com/zhangyuntaoshe/articles/123066.html  

合并两张bit图到一张p_w_picpath的方法

  1. To graphically merge two p_w_picpaths into a new p_w_picpath, you do something like this:    
  2. UIImage *result = nil;    
  3. unsignedchar *data = calloc(1,size.width*size.height*kBytesPerPixel);    
  4. if (data != NULL) {    
  5. // kCGImageAlphaPremultipliedLast 为预记录的#define value    
  6. // 设置context上下文    
  7. CGContextRef context = CGBitmapContextCreate(    
  8. data, size.width, size.height, 8, size.width*kBytesPerPixel,    
  9. CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast);    
  10. if (context != NULL) {    
  11. UIGraphicsPushContext(context);    
  12. //  Image 为下载的背景图片,用于比较context    
  13. CGContextTranslateCTM(context, 0, size.height);    
  14. CGContextScaleCTM(context, 1, -1);    
  15. [p_w_picpath drawInRect:p_w_picpathRect];    
  16. [p_w_picpath2 drawInRect:p_w_picpath2Rect];    
  17. UIGraphicsPopContext();    
  18. CGImageRef p_w_picpathRef = CGBitmapContextCreateImage(context);    
  19. if (p_w_picpathRef != NULL) {    
  20. result = [UIImagep_w_picpathWithCGImage:p_w_picpathRef];    
  21. CGImageRelease(p_w_picpathRef);    
  22. }    
  23. CGContextRelease(context);    
  24. }    
  25. free(data);    
  26. }    
  27. return result;  

关键方法： 

  1. CGContextRef context = CGBitmapContextCreate();    
  2. CGContextTranslateCTM();    
  3. CGContextScaleCTM();    
  4. CGImageRef p_w_picpathRef = CGBitmapContextCreateImage(context);    
  5. CGImageRelease(p_w_picpathRef);