IOS开发之—绘图 CGContext

iPhone图形开发绘图教程是本文要介绍的内容，介绍了很多关于绘图类的使用，先来看详细内容讲解。



1、绘图总结:

绘图前设置:

CGContextSetRGBFillColor/CGContextSetFillColorWithColor  //填充色    
CGContextSetRGBStrokeColor/CGContextSetStrokeColorWithColor //笔颜色    
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:

CGContextFillRect/CGContextFillRects    
CGContextFillEllipseInRect    
CGContextAddRect/CGContextAddRects    
CGContextAddEllipseInRect    
CGContextAddLines    
CGContextMoveToPoint    
CGContextAddLineToPoint

3.常见控制方法:

CGContextSaveGState    
CGContextRestoreGState

4.创建内存图像context:

CGBitmapContextCreate       <-----CGContextRlease释放    
CGColorSpaceCreateWithName    (KCGColorSpaceGenericRGB)    
CGColorSpaceRlease    
CGBitmapContextCreateImage()   <-----CGImageRlease 释放.    
eg:    
CGContextRefMyCreateBitmapContext(intpixelsWide,intpixelsHigh)    
{    
CGContextRef    context=NULL;    
CGColorSpaceRefcolorSpace;    
void*          bitmapData;    
int             bitmapByteCount;    
int             bitmapBytesPerRow;    
bitmapBytesPerRow   =(pixelsWide*4);    
bitmapByteCount     =(bitmapBytesPerRow*pixelsHigh);    
colorSpace=CGColorSpaceCreateDeviceRGB();    
bitmapData=malloc(bitmapByteCount);    
if(bitmapData==NULL)    
{    
fprintf(stderr,"Memorynotallocated!");    
returnNULL;    
}    
context=CGBitmapContextCreate(bitmapData,    
 pixelsWide,    pixelsHigh,    8,     
bitmapBytesPerRow,    colorSpace,    
 kCGImageAlphaPremultipliedLast);    
if(context==NULL)    
{    
free(bitmapData);    
fprintf(stderr,"Contextnotcreated!");    
returnNULL;    
}    
CGColorSpaceRelease(colorSpace);    
returncontext;    
}

5.图形的变换:

CGContextTranslateCTM    
CGContextRotateCTM    
CGContextScaleCTM

6.常用函数:

CGRectContainsPoint();    
CGRectContainsRect();    
CGRectIntersectsRect();    
CGRectIntersection();    
CGPointEqualToPoint();    
CGSizeEqualToSize();

7.从原图片中取小图.

CGImageCreateWithImageInRect

8.屏幕快照:

#import "QuartzCore/QuartzCore.h"    
  
UIGraphicsBeginImageContext(yourView.frame.size);    
[[yourView layer] renderInContext:UIGraphicsGetCurrentContext()];    
UIImage*screenshot =UIGraphicsGetImageFromCurrentImageContext();    
UIGraphicsEndImageContext();    
from:http://www.cppblog.com/zhangyuntaoshe/articles/123066.html

合并两张bit图到一张image的方法

To graphically merge two images into a new image, you do something like this:    
UIImage *result = nil;    
unsignedchar *data = calloc(1,size.width*size.height*kBytesPerPixel);    
if (data != NULL) {    
// kCGImageAlphaPremultipliedLast 为预记录的#define value    
// 设置context上下文    
CGContextRef context = CGBitmapContextCreate(    
data, size.width, size.height, 8, size.width*kBytesPerPixel,    
CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast);    
if (context != NULL) {    
UIGraphicsPushContext(context);    
//  Image 为下载的背景图片,用于比较context    
CGContextTranslateCTM(context, 0, size.height);    
CGContextScaleCTM(context, 1, -1);    
[image drawInRect:imageRect];    
[image2 drawInRect:image2Rect];    
UIGraphicsPopContext();    
CGImageRef imageRef = CGBitmapContextCreateImage(context);    
if (imageRef != NULL) {    
result = [UIImageimageWithCGImage:imageRef];    
CGImageRelease(imageRef);    
}    
CGContextRelease(context);    
}    
free(data);    
}    
return result;

关键方法：

CGContextRef context = CGBitmapContextCreate();    
CGContextTranslateCTM();    
CGContextScaleCTM();    
CGImageRef imageRef = CGBitmapContextCreateImage(context);    
CGImageRelease(imageRef);

小结：iPhone图形开发绘图教程的内容介绍完了，希望本文对你有所帮助！

http://blog.csdn.net/pjk1129/article/details/7161383