前段时间只看，没有手动写过代码，今天无聊就写了一个画聊天对话框的例子，其实还是蛮实用的，以后一定会有用到的地方。
主要用到Quartz的几个关键技术
路径，阴影，填充，描边，图像上下文环境的设置。
以下是代码：
CGContextRef MyCreateBitmapContext (int pixelsWide
int pixelsHigh)
{
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
//声明一个变量来代表每行的字节数。每一个位图像素的代表是4个字节，8bit红，8bit绿，8bit蓝，和8bit alpha通道信息(透明信息)。
bitmapBytesPerRow = (pixelsWide * 4);
bitmapByteCount = (bitmapBytesPerRow * pixelsHigh);
colorSpace = CGColorSpaceCreateDeviceRGB();// 创建一个通用的RGB色彩空间
bitmapData = malloc( bitmapByteCount );// 调用的malloc函数来创建的内存用来存储位图数据块
if (bitmapData == NULL)
{
fprintf (stderr "Memory not allocated!");
return NULL;
}
//创建一个位图图形上下文
context = CGBitmapContextCreate (bitmapData
pixelsWide
pixelsHigh
8 // bits per component
bitmapBytesPerRow
colorSpace
kCGImageAlphaPremultipliedLast);
if (context== NULL)
{
free (bitmapData);
fprintf (stderr "Context not created!");
return NULL;
}
//释放colorSpace 注意使用的函数
CGColorSpaceRelease( colorSpace );
return context;
}
/*
生成一个聊天的对话框背景图
参数
myContext:一个图形上下文
ox: 矩形左下角x坐标
oy: 矩形左下角y坐标
rw: 矩形宽度
rh: 矩形高度
r : 矩形圆角半径
Orientation: 箭头方向，0-7
*/
UIImage* createDialogBox (CGContextRef myContext float ox float oy float rw float rh float r int Orientation)
{
CGMutablePathRef path = CGPathCreateMutable();
//画矩形
CGPathMoveToPoint(path NULLox oy+r);
CGPathAddArcToPoint(path NULL ox oy+rh ox+roy+rh r);
CGPathAddArcToPoint(path NULL ox+rw oy+rh ox+rw oy+rh-r r);
CGPathAddArcToPoint(path NULL ox+rw oy ox+rw-r oy r);
CGPathAddArcToPoint(path NULL ox oy oxoy+rr);
//画箭头
switch (Orientation) {
case 0:
CGPathMoveToPoint(path NULLox+r+10.0 oy+rh);
CGPathAddLineToPoint(path NULL ox+r+10.0 oy+rh+20);
CGPathAddLineToPoint(path NULL ox+r+30.0 oy+rh);
break;
case 1:
CGPathMoveToPoint(path NULLox+rw-r-10.0 oy+rh);
CGPathAddLineToPoint(path NULL ox+rw-r-10.0 oy+rh+20);
CGPathAddLineToPoint(path NULL ox+rw-r-30.0 oy+rh);
break;
case 2:
CGPathMoveToPoint(path NULLox+rw oy+rh-r-10);
CGPathAddLineToPoint(path NULL ox+rw+20 oy+rh-r-10);
CGPathAddLineToPoint(path NULL ox+rw oy+rh-r-30);
break;
case 3:
CGPathMoveToPoint(path NULLox+rw oy+r+10);
CGPathAddLineToPoint(path NULL ox+rw+20 oy+r+10);
CGPathAddLineToPoint(path NULL ox+rw oy+r+30);
break;
case 4:
CGPathMoveToPoint(path NULLox+rw-r-10.0 oy);
CGPathAddLineToPoint(path NULL ox+rw-r-10.0 oy-20);
CGPathAddLineToPoint(path NULL ox+rw-r-30.0 oy);
break;
case 5:
CGPathMoveToPoint(path NULLox+r+10.0 oy);
CGPathAddLineToPoint(path NULL ox+r+10.0 oy-20);
CGPathAddLineToPoint(path NULL ox+r+30.0 oy);
break;
case 6:
CGPathMoveToPoint(path NULLox oy+r+10);
CGPathAddLineToPoint(path NULL ox-20 oy+r+10);
CGPathAddLineToPoint(path NULL ox oy+r+30);
break;
case 7:
CGPathMoveToPoint(path NULLox oy+rh-r-10);
CGPathAddLineToPoint(path NULL ox-20 oy+rh-r-10);
CGPathAddLineToPoint(path NULL ox oy+rh-r-30);
break;
default:
break;
}
//描边 以及添加阴影效果
CGContextSetLineJoin(myContext kCGLineJoinRound);
CGFloat zStrokeColour[4] = {180.0/255 180.0/255.0 180.0/255.0 1.0};
CGContextSetLineWidth(myContext 13.0);
CGContextAddPath(myContextpath);
CGContextSetStrokeColorSpace(myContext CGColorSpaceCreateDeviceRGB());
CGContextSetStrokeColor(myContext zStrokeColour);
CGContextStrokePath(myContext);
CGSize myShadowOffset = CGSizeMake (0 0);
CGContextSaveGState(myContext);
CGContextSetShadow (myContext myShadowOffset 5);
CGContextSetLineJoin(myContext kCGLineJoinRound);
CGFloat zStrokeColour1[4] = {228.0/255 168.0/255.0 81.0/255.0 1.0};
CGContextSetLineWidth(myContext 3.0);
CGContextAddPath(myContextpath);
CGContextSetStrokeColorSpace(myContext CGColorSpaceCreateDeviceRGB());
CGContextSetStrokeColor(myContext zStrokeColour1);
CGContextStrokePath(myContext);
CGContextRestoreGState(myContext);
//填充矩形内部颜色
CGContextAddPath(myContextpath);
CGContextSetFillColorSpace(myContext CGColorSpaceCreateDeviceRGB());
CGFloat zFillColour1[4] = {229.0/255 229.0/255.0 231.0/255.0 1};
CGContextSetFillColor(myContext zFillColour1);
CGContextEOFillPath(myContext);
//生成图像
CGImageRef myImage = CGBitmapContextCreateImage (myContext);
UIImage * image = [UIImage imageWithCGImage:myImage];
CGImageRelease(myImage);
return image;
}
- (void)viewDidLoad {
[super viewDidLoad];
float wd = 320.0;
float ht = 480.0;
CGContextRef myContext = MyCreateBitmapContext (wd ht);
UIImageView *iv = [[UIImageView alloc] initWithImage:createDialogBox(myContext 50 350 100 60 5 7)];
[self.view addSubview:iv];