今天写了个将文字转化为多彩图片的功能，输入文字将文字转化为彩色的文字图片，可选择不同的字体，渐变，先看看效果。

屏幕快照 2016-01-12 上午9.42.23.png

实现主要用CAGradientLayer渐变，先看看上部展示实现代码：

-(void)setupContentView
{
    UIView *contentView = [[UIView alloc] initWithFrame:CGRectMake(0, 44, ScreenWidth, ScreenHight - 44 -300)];
    [self.view addSubview:contentView];
    UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapGestureAction:)];
    [contentView addGestureRecognizer:tapGesture];
    self.topContentView = contentView;
    self.topContentView.backgroundColor = [UIColor clearColor];
    
    UILabel *label = [[UILabel alloc] init];
    label.numberOfLines = 0;
    label.text = @"ABC";
    label.frame = [self calculateContextLabelFrameWithTitle:@"ABC"];
    label.center = CGPointMake(contentView.bounds.size.width / 2, contentView.bounds.size.height / 2);
    label.font = [UIFont fontWithName:self.fontNameArray[0] size:25];
    label.textAlignment = NSTextAlignmentCenter;
    [contentView addSubview:label];
    label.backgroundColor = [UIColor clearColor];
    self.contentLabel = label;
    
    self.gradientLayer = [CAGradientLayer layer];
    self.gradientLayer.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, label.frame.size.width, label.frame.size.height);
    self.gradientLayer.backgroundColor = [UIColor clearColor].CGColor;
    self.gradientLayer.startPoint = CGPointMake(0,0.5);
    self.gradientLayer.endPoint = CGPointMake(1,0.5);
    self.gradientLayer.colors = self.grandentArr[0];
    [contentView.layer addSublayer:self.gradientLayer];
    self.gradientLayer.mask = self.contentLabel.layer;
    self.contentLabel.frame = self.gradientLayer.bounds;
}

当输入的文字改变时，重新计算 self.gradientLayer的frame

-(void)textFieldTextChange:(NSNotification*)notice
{
    self.contentLabel.text = self.textField.text;
    [self reCalculateGradientLayerFrame];
}

下部分的实现代码：

-(void)setupBottomView
{
    UIView *bottomView =[[UIView alloc] initWithFrame:CGRectMake(0, ScreenHight - 300, ScreenWidth, 300)];
    bottomView.backgroundColor = JGCOLOR(222, 222, 222);
    [self.view addSubview:bottomView];
    self.bottomContentView = bottomView;
    
    UIView *textContentView = [[UIView alloc] init];
    textContentView.frame = CGRectMake(0, 0, bottomView.bounds.size.width, 50);
    [bottomView addSubview:textContentView];
    textContentView.backgroundColor = JGCOLOR(55, 44, 16);
    
    UITextField *textField = [[UITextField alloc] init];
    textField.borderStyle = UITextBorderStyleRoundedRect;
    textField.frame = CGRectMake(10, 5, textContentView.bounds.size.width - 20, textContentView.bounds.size.height - 10);
    [textContentView addSubview:textField];
    self.textField = textField;
    
    CGFloat orgY = 60;
    CGFloat orgx = 10;
    CGFloat space = 10;
    CGFloat width = (ScreenWidth - orgx * 2 - 3 * space) / 4;
    CGFloat height = 35;
    
    for (int i = 0; i < 16; i++) {
        UIView *vw = [[UIView alloc] initWithFrame:CGRectMake(orgx + (i % 4) * width + (i % 4) * space, orgY + (i / 4) * height + (i / 4) * space, width, height)];
        vw.backgroundColor = [UIColor clearColor];
        vw.tag = i + 1;
        [self.bottomContentView addSubview:vw];
        
        UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewTap:)];
        [vw addGestureRecognizer:tapGesture];
        
        UILabel *label = [[UILabel alloc] initWithFrame:vw.bounds
                          ];
        label.textAlignment = NSTextAlignmentCenter;
        label.text = @"ABC";
        label.frame = vw.bounds;
        label.font = [UIFont fontWithName:self.fontNameArray[i % 4] size:25];
        label.backgroundColor = [UIColor clearColor];
        [vw addSubview:label];
        
        CAGradientLayer *grandient = [CAGradientLayer layer];
        grandient.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, label.frame.size.width, label.frame.size.height);
        grandient.backgroundColor = [UIColor clearColor].CGColor;
        grandient.startPoint = CGPointMake(0,0.5);
        grandient.endPoint = CGPointMake(1,0.5);
        grandient.colors = self.grandentArr[i / 4];
        [vw.layer addSublayer:grandient];
        grandient.mask = label.layer;
        label.frame = grandient.bounds;
    }
}

将文字转化为图片的代码：

-(void)getTitleImg
{
    UIGraphicsBeginImageContext(self.topContentView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    if ([[UIDevice currentDevice].systemVersion floatValue] >= 7.0) {
        [self.topContentView drawViewHierarchyInRect:self.topContentView.frame afterScreenUpdates:YES];
    }
    else
    {
        [self.topContentView.layer renderInContext:context];
    }
    
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    CGImageRef newImgRef =  CGImageCreateWithImageInRect(img.CGImage, CGRectMake(self.gradientLayer.frame.origin.x, self.gradientLayer.frame.origin.y + 44, self.gradientLayer.frame.size.width, self.gradientLayer.frame.size.height));
    
    UIGraphicsBeginImageContextWithOptions(self.gradientLayer.frame.size, NO, [UIScreen mainScreen].scale);
    context = UIGraphicsGetCurrentContext();
    
    CGContextTranslateCTM(context, 0, self.gradientLayer.frame.size.height);
    CGContextScaleCTM(context, 1, -1);
    
    CGContextDrawImage(context, CGRectMake(0, 0, self.gradientLayer.frame.size.width, self.gradientLayer.frame.size.height), newImgRef);
    UIImage *newImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library toolWriteImageToSavedPhotosAlbum:newImg.CGImage metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
        
        if (error) {
            JGLog(@"写入出错");
        }
    } groupName:@"相册名称"];
    
}

核心代码如上，主要运用到了CAGradientLayer,截图，裁图的方法。上传代码github：https://github.com/jiangtaidi/titleImgCreateDemo.git