如何在 Objective-C (iOS) 中在图像上写入文本？

Question

提问by Sanchit Paurush

I want to make an image like this programmatically:

我想以编程方式制作这样的图像：

example

I have the upper image and text with me. Should I write text on the image?

我有上面的图片和文字。我应该在图像上写文字吗？

I want to make it a complete .png image(image + label) and set it as the background of the button.

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

回答by Jano

Draw text inside an image and return the resulting image:

在图像内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;
}

Usage:

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)];

Change the origin of the text inside the image from 0,0 to whatever point you like.

将图像内文本的原点从 0,0 更改为您喜欢的任何点。

To paint a rectangle of solid color behind the text, add the following before the line [[UIColor whiteColor] set];:

要在文本后面绘制一个纯色矩形，请在行之前添加以下内容[[UIColor whiteColor] set];：

[[UIColor brownColor] set];
CGContextFillRect(UIGraphicsGetCurrentContext(), 
                  CGRectMake(0, (image.size.height-[text sizeWithFont:font].height), 
                                  image.size.width, image.size.height));

I'm using the text size to calculate the origin for the solid color rectangle, but you can replace it with any number.

我使用文本大小来计算纯色矩形的原点，但您可以将其替换为任何数字。

Answer 2

回答by iGranDav

My contribution to the first answer with iOS 7 support :

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;
}

Hope this helps

希望这可以帮助

EDIT:modified the UIGraphicsBeginImageContextWithOptionsto handle screen scale. Thk @SoftDesigner

编辑：修改UIGraphicsBeginImageContextWithOptions处理屏幕比例。思念@SoftDesigner

Answer 3

回答by Christopher Wade Cantley

Here is the Swift version.

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

}

To call it you just pass in an image.

要调用它，您只需传入一个图像。

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

The following links helped me get this straight.