IOS開發——繪圖

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

一、繪圖總結:

繪圖前設置:

CGContextSetRGBFillColor/CGContextSetFillColorWithColor  //填充色
CGContextSetRGBStrokeColor/CGContextSetStrokeColorWithColor //筆顏色
CGContextSetLineWidth   //線寬度

繪圖後設置:

注:  畫完圖後,必須 先用CGContextStrokePath來描線,即形狀，後用CGContextFillPath來填充形狀內的顏色.

2.常見圖形繪製:

CGContextFillRect/CGContextFillRects
CGContextFillEllipseInRect
CGContextAddRect/CGContextAddRects
CGContextAddEllipseInRect
CGContextAddLines
CGContextMoveToPoint
CGContextAddLineToPoint

3.常見控制方法:

CGContextSaveGState
CGContextRestoreGState

4.建立內存圖像context:

CGBitmapContextCreate       <-----CGContextRlease釋放
CGColorSpaceCreateWithName    (KCGColorSpaceGenericRGB)
CGColorSpaceRlease
CGBitmapContextCreateImage()   <-----CGImageRlease 釋放.
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.圖形的變換:

CGContextTranslateCTM
CGContextRotateCTM
CGContextScaleCTM

6.經常使用函數:

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

7.從原圖片中取小圖.

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

合併兩張bit圖到一張p_w_picpath的方法

To graphically merge two p_w_picpaths into a new p_w_picpath, you do something like this:
UIImage *result = nil;
unsignedchar *data = calloc(1,size.width*size.height*kBytesPerPixel);
if (data != NULL) {
// kCGImageAlphaPremultipliedLast 爲預記錄的#define value
// 設置context上下文
CGContextRef context = CGBitmapContextCreate(
data, size.width, size.height, 8, size.width*kBytesPerPixel,
CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast);
if (context != NULL) {
UIGraphicsPushContext(context);
//  Image 爲下載的背景圖片,用於比較context
CGContextTranslateCTM(context, 0, size.height);
CGContextScaleCTM(context, 1, -1);
[p_w_picpath drawInRect:p_w_picpathRect];
[p_w_picpath2 drawInRect:p_w_picpath2Rect];
UIGraphicsPopContext();
CGImageRef p_w_picpathRef = CGBitmapContextCreateImage(context);
if (p_w_picpathRef != NULL) {
result = [UIImagep_w_picpathWithCGImage:p_w_picpathRef];
CGImageRelease(p_w_picpathRef);
}
CGContextRelease(context);
}
free(data);
}
return result;

關鍵方法：

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