如何在Objective-C（iOS）中的图像上写文字？

Question

我想以编程方式制作这样的图像：我有上面的图像和文字。我应该在图像上写文字吗？我想让它成为一个完整的.png图像（图像+标签）并将其设置为按钮的背景。

Answer 1

在图像中绘制文本并返回结果图像：

+(UIImage*) drawText:(NSString*) text 

             inImage:(UIImage*)  image 

             atPoint:(CGPoint)   point 

{

    UIFont *font = [UIFont boldSystemFontOfSize:12];

    UIGraphicsBeginImageContext(image.size);

    [image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];

    CGRect rect = CGRectMake(point.x, point.y, image.size.width, image.size.height);

    [[UIColor whiteColor] set];

    [text drawInRect:CGRectIntegral(rect) withFont:font]; 

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;

}

用法：

// note: replace "ImageUtils" with the class where you pasted the method above

UIImage *img = [ImageUtils drawText:@"Some text"

                            inImage:img 

                            atPoint:CGPointMake(0, 0)];

将图像内部文本的原点从0,0更改为您喜欢的任何点。

要在文本后面绘制纯色矩形，请在行前添加以下内容[[UIColor whiteColor] set];：

[[UIColor brownColor] set];

CGContextFillRect(UIGraphicsGetCurrentContext(), 

                  CGRectMake(0, (image.size.height-[text sizeWithFont:font].height), 

                                  image.size.width, image.size.height));

我正在使用文本大小来计算纯色矩形的原点，但您可以用任何数字替换它。

Answer 2

我对iOS 7支持的第一个答案的贡献：

+(UIImage*) drawText:(NSString*) text

             inImage:(UIImage*)  image

             atPoint:(CGPoint)   point

{

    UIGraphicsBeginImageContextWithOptions(image.size, YES, 0.0f);

    [image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];

    CGRect rect = CGRectMake(point.x, point.y, image.size.width, image.size.height);

    [[UIColor whiteColor] set];

    UIFont *font = [UIFont boldSystemFontOfSize:12];

    if([text respondsToSelector:@selector(drawInRect:withAttributes:)])

    {

        //iOS 7

        NSDictionary *att = @{NSFontAttributeName:font};

        [text drawInRect:rect withAttributes:att];

    }

    else

    {

        //legacy support

        [text drawInRect:CGRectIntegral(rect) withFont:font];

    }

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return newImage;

}

希望这可以帮助

编辑：修改了UIGraphicsBeginImageContextWithOptions处理屏幕比例。

Answer 3

这是Swift版本。

func textToImage(drawText: NSString, inImage: UIImage, atPoint:CGPoint)->UIImage{

    // Setup the font specific variables

    var textColor: UIColor = UIColor.whiteColor()

    var textFont: UIFont = UIFont(name: "Helvetica Bold", size: 12)!

    //Setup the image context using the passed image.

    UIGraphicsBeginImageContext(inImage.size)

    //Setups up the font attributes that will be later used to dictate how the text should be drawn

    let textFontAttributes = [

        NSFontAttributeName: textFont,

        NSForegroundColorAttributeName: textColor,

    ]

    //Put the image into a rectangle as large as the original image.

    inImage.drawInRect(CGRectMake(0, 0, inImage.size.width, inImage.size.height))

    // Creating a point within the space that is as bit as the image.

    var rect: CGRect = CGRectMake(atPoint.x, atPoint.y, inImage.size.width, inImage.size.height)

    //Now Draw the text into an image.

    drawText.drawInRect(rect, withAttributes: textFontAttributes)

    // Create a new image out of the images we have created

    var newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()

    // End the context now that we have the image we need

    UIGraphicsEndImageContext()

    //And pass it back up to the caller.

    return newImage

}

要调用它，您只需传入一个图像。

textToImage("000", inImage: UIImage(named:"thisImage.png")!, atPoint: CGPointMake(20, 20))

以下链接帮助我顺利完成。

Swift - 使用drawInRect绘制文本：withAttributes：

如何在Objective-C（iOS）中的图像上写文字？

最初的目标是创建一个动态图像，我可以在AnnotaionView中使用它，例如在地图上的给定位置定价，这对它来说非常有用。希望这有助于某人尝试做同样的事情。