iOS图片拼接，图片文字合成总结

1. 注意事项：项目报错，图片模糊，内存问题，离屏渲染
2. 以下是合成的步骤：
   1. 先读取两张图片把创建出CGImageRef
   2. 创建上下文画布
   3. 把图片依次画在画布指定位置上
   4. 从上下文中获得合并后的图片
   5. 关闭上下文
   6. 释放内存
   7. 
      

   两张图片合成：- (void)composeImg {
   UIImage *img = [UIImage imageNamed:@"0.png"];
   CGImageRef imgRef = img.CGImage;
   CGFloat w = CGImageGetWidth(imgRef);
   CGFloat h = CGImageGetHeight(imgRef);
   
   //以1.png的图大小为底图
   UIImage *img1 = [UIImage imageNamed:@"1.png"];
   CGImageRef imgRef1 = img1.CGImage;
   CGFloat w1 = CGImageGetWidth(imgRef1);
   CGFloat h1 = CGImageGetHeight(imgRef1);
   
   //以1.png的图大小为画布创建上下文
   UIGraphicsBeginImageContext(CGSizeMake(w1, h1));
       [img1 drawInRect:CGRectMake(0, 0, w1, h1)];//先把1.png 画到上下文中
       [img drawInRect:CGRectMake(100, 100, w, h)];//再把小图放在上下文中
   UIImage *resultImg = UIGraphicsGetImageFromCurrentImageContext();//从当前上下文中获得最终图片
   UIGraphicsEndImageContext();//关闭上下文
   
   NSString *path = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
   NSString *filePath = [path stringByAppendingPathComponent:@"01.png"];
       [UIImagePNGRepresentation(resultImg) writeToFile:filePath atomically:YES];//保存图片到沙盒
   
   CGImageRelease(imgRef);
   CGImageRelease(imgRef1);
   }

   图片与文字合成：-(UIImage *)CSImage:(UIImage *)img AddText:(NSString *)text
   {
   
       UIImageView *view = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, img.size.width, img.size.height)];
       view.image = img;
   
   
   
       UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,0,0)];
   
       [label setNumberOfLines:0];
       label.lineBreakMode = UILineBreakModeWordWrap;
   
       NSString *s = text;
       UIFont *font = [UIFont fontWithName:@"Arial" size:12];
   
       CGSize size = CGSizeMake(320,2000);
   
       CGSize labelsize = [s sizeWithFont:font constrainedToSize:size lineBreakMode:UILineBreakModeWordWrap];
       label.frame = CGRectMake(0,0, labelsize.width, labelsize.height);
   
       [view addSubview:label];
   
       return [self convertViewToImage:view];
   }
   
   -(UIImage*)convertViewToImage:(UIView*)v
   {
       CGSize s = v.bounds.size;
   
   
   
       UIGraphicsBeginImageContextWithOptions(s, NO, [UIScreen mainScreen].scale);
   
       CGContextRef context = UIGraphicsGetCurrentContext();
   
       [v.layer renderInContext:context];
   
       UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
       UIGraphicsEndImageContext();
   
       v.layer.contents = nil;
       return image;
   
   }

   图片模糊问题，解决方法：1本身图片有问题，2图片压缩的太狠了，3使用WithOptions函数

   
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