生成带文本的UIImage

-(UIImage *)createTextImg:(NSString *)imgName text:(NSString *)text1{
    
    UIImage* img = [UIImage imageNamed:imgName];
    NSAssert(img, @"");
    int w = img.size.width;
    int h = img.size.height;
    
    float scale = img.scale;
    w *= scale;
    h *= scale;
    
    // 画图
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
    CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
    
    // 画文本
    CTFontRef ctfont = CTFontCreateWithName(CFSTR("ArialMT"), 16 * scale, NULL);
    CGColorRef ctColor = [[UIColor whiteColor] CGColor];
    
    CFStringRef keys[] = { kCTFontAttributeName,kCTForegroundColorAttributeName };
    CFTypeRef values[] = { ctfont,ctColor};
    CFDictionaryRef attr = CFDictionaryCreate(NULL, (const void **)&keys, (const void **)&values,
                                              sizeof(keys) / sizeof(keys[0]), &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    
    
    CFStringRef ctStr = CFStringCreateWithCString(nil, [text1 UTF8String], kCFStringEncodingUTF8);
    CFAttributedStringRef attrString = CFAttributedStringCreate(NULL,ctStr, attr);
    CTLineRef line = CTLineCreateWithAttributedString(attrString);
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextSetTextPosition(context, 4 * scale, 22 * scale);
    CTLineDraw(line, context);
    
    CFRelease(line);
    CFRelease(attrString);
    CFRelease(ctStr);
    
    CGImageRef imageMasked = CGBitmapContextCreateImage(context);
    
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    UIImage *image =[UIImage imageWithCGImage:imageMasked scale:scale orientation:img.imageOrientation];
    CFRelease(imageMasked);
    return image;
}