如何在 Objective-C (iOS)中在图像上写文本？

小开

UIImageView *imageView = [UIImageView alloc];
imageView.image = [UIImage imageNamed:@"img.png"];
UILabel *label = [UILabel alloc];
label.text = @"Your text";
[imageView addsubview:label];

将标签的框架设置为要显示标签的位置。

小开

最佳答案

Draw text inside an image and return the resulting image:

+(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)];

将图像中文本的原点从0,0更改为您喜欢的任意点。

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

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

我使用文本大小来计算纯色矩形的原点，但是您可以用任意数字替换它。

小开

在浏览并结合了一些例子之后，我做了这样的事情。

Puts the text in the midle of the image, resizing the font if needed.

UIImage *myImage = [UIImage imageNamed:@"promoicon.png"];
UIGraphicsBeginImageContext(myImage.size);
[myImage drawInRect:CGRectMake(0,0,myImage.size.width,myImage.size.height)];
UITextView *myText = [[UITextView alloc] init];
myText.font = [UIFont fontWithName:@"TrebuchetMS-Bold" size:15.0f];
myText.textColor = [UIColor whiteColor];
myText.text = NSLocalizedString(@"promotionImageText", @"");
myText.backgroundColor = [UIColor clearColor];


CGSize maximumLabelSize = CGSizeMake(myImage.size.width,myImage.size.height);
CGSize expectedLabelSize = [myText.text sizeWithFont:myText.font
constrainedToSize:maximumLabelSize
lineBreakMode:UILineBreakModeWordWrap];


myText.frame = CGRectMake((myImage.size.width / 2) - (expectedLabelSize.width / 2),
(myImage.size.height / 2) - (expectedLabelSize.height / 2),
myImage.size.width,
myImage.size.height);


[[UIColor whiteColor] set];
[myText.text drawInRect:myText.frame withFont:myText.font];
UIImage *myNewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

小开

只有 iOS7。

Watermark in lower right corner.

@interface UIImage (DrawWatermarkText)
-(UIImage*)drawWatermarkText:(NSString*)text;
@end
@implementation UIImage (DrawWatermarkText)
-(UIImage*)drawWatermarkText:(NSString*)text {
UIColor *textColor = [UIColor colorWithWhite:0.5 alpha:1.0];
UIFont *font = [UIFont systemFontOfSize:50];
CGFloat paddingX = 20.f;
CGFloat paddingY = 20.f;


// Compute rect to draw the text inside
CGSize imageSize = self.size;
NSDictionary *attr = @{NSForegroundColorAttributeName: textColor, NSFontAttributeName: font};
CGSize textSize = [text sizeWithAttributes:attr];
CGRect textRect = CGRectMake(imageSize.width - textSize.width - paddingX, imageSize.height - textSize.height - paddingY, textSize.width, textSize.height);


// Create the image
UIGraphicsBeginImageContext(imageSize);
[self drawInRect:CGRectMake(0, 0, imageSize.width, imageSize.height)];
[text drawInRect:CGRectIntegral(textRect) withAttributes:attr];
UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultImage;
}
@end

用法:

UIImage *image = [UIImage imageNamed:@"mona_lisa"];
image = [image drawWatermarkText:@"Leonardo da Vinci"];

小开

我对第一个答案的贡献与 iOS7的支持:

+(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;
}

希望这个能帮上忙

编辑: 修改了 UIGraphicsBeginImageContextWithOptions来处理屏幕缩放

小开

这是斯威夫特的版本。

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


}