IOS开发－画线画图

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();

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);