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);

9.图片变小

1 - (UIImage *)transformToSize(CGSize)newSize{
   2 UIGraphicsBeginImageContext(newSize); 3 [self drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; 4 UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext(); 5 UIGraphicsEndImageContext(); 6 return scaledImage; 7 }