Detailed explanation of Imagick PHP extension library: Add text watermark to images

This article will introduce how to add text watermarks to images using PHP's Imagick extension library. We will explore a variety of methods, including simple text overlay, creating transparent text watermarks using font masks, and more advanced text tiling techniques.

Key points:

• Imagick is a powerful PHP extension library that can be used to process images, including adding text watermarks.
• Text watermarking can be achieved by creating an Imagick class instance, reading an image, setting the font properties using the ImagickDraw instance, and then adding text to the image using the annotateImage() method.
• There are several ways to add text watermarks, including overlaying text strings directly on the image, creating transparent text watermarks with font masks, and tiling text across the entire image to make watermark removal difficult.
• ImagickDraw class provides multiple ways to customize watermark text, such as setFillColor()change font color, setFontSize()change font size, setFont()change font, setFillOpacity()add transparency, and annotateImage()position and rotate text .

In previous articles, Timothy Boronczyk described how to create watermarks using Imagick and overlay images. This article will show how to achieve similar effects using plain text. Currently, PHP's Imagick API documentation is very scarce, but there are many command line examples on the ImageMagick website, which we will start with. Converting command line code to PHP code is just a matter of finding the corresponding method to perform the same function. The following example will use a random handsome guy picture.

Draw text on image

The easiest text watermark is to overlay strings directly on the image. The command line example is as follows:

convert image.png  -font Arial -pointsize 20 \
    -draw "gravity south \
        fill black  text 0,12 'Copyright' \
        fill white  text 1,11 'Copyright'" \
    result.png

Responsive PHP code:

<?php 
// 創(chuàng)建對象
$image = new Imagick('image.png');

// 水印文本
$text = 'Copyright';

// 創(chuàng)建新的繪圖面板
$draw = new ImagickDraw();

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('black');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在圖像上繪制文本
$image->annotateImage($draw, 10, 12, 0, $text);

// 稍微偏移位置，使用不同的顏色再次繪制文本
$draw->setFillColor('white');
$image->annotateImage($draw, 11, 11, 0, $text);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Reproduction picture:

This example is very simple and the code comments are very clear. Although effective, the contrast between text and image is too strong and the effect is not soft enough.

Create transparent text using font mask

To make the watermark text more soft, you can use a font mask to create transparent text. Command line example:

convert -size 300x50 xc:grey30 -font Arial -pointsize 20 \
    -gravity center -draw "fill grey70  text 0,0  'Copyright'" \
    fgnd.png
convert -size 300x50 xc:black -font Arial -pointsize 20 -gravity center \
    -draw "fill white  text  1,1  'Copyright' \
        text  0,0  'Copyright' \
        fill black  text -1,-1 'Copyright'" \
    +matte mask.png
composite -compose CopyOpacity  mask.png  fgnd.png  stamp.png 
    mogrify -trim +repage stamp.png
composite -gravity south -geometry +0+10 stamp.png  image.png \
    result.png

PHP Code:

<?php
// 創(chuàng)建對象
$image = new Imagick('image.png');
$watermark = new Imagick();
$mask = new Imagick();
$draw = new ImagickDraw();

// 定義尺寸
$width = $image->getImageWidth();
$height = $image->getImageHeight();

// 創(chuàng)建調(diào)色板
$watermark->newImage($width, $height, new ImagickPixel('grey30'));
$mask->newImage($width, $height, new ImagickPixel('black'));

// 水印文本
$text = 'Copyright';

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('grey70');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在水印調(diào)色板上繪制文本
$watermark->annotateImage($draw, 10, 12, 0, $text);

// 在蒙版調(diào)色板上繪制文本
$draw->setFillColor('white');
$mask->annotateImage($draw, 11, 13, 0, $text);
$mask->annotateImage($draw, 10, 12, 0, $text);
$draw->setFillColor('black');
$mask->annotateImage($draw, 9, 11, 0, $text);

// 這是蒙版生效的必要條件
$mask->setImageMatte(false);

// 將蒙版應(yīng)用于水印
$watermark->compositeImage($mask, Imagick::COMPOSITE_COPYOPACITY, 0, 0);

// 將水印疊加到圖像上
$image->compositeImage($watermark, Imagick::COMPOSITE_DISSOLVE, 0, 0);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Reproduction picture:

This example creates multiple images. The first image $watermark is a grayscale image, the second image $mask uses pure black to represent the part to be transparent and white to represent the part to be retained. When applying masks through a combination image, any gray shadows found in $mask due to anti-aliasing effects will be translucent, resulting in smoother edges. In the command line version code, the outer edges of the transparent image are cropped before overlaying the watermark, but there seems to be a bug that prevents the compositeImage() method from retaining the location defined by the setGravity(). This means that if the edge is cropped, the watermark will lose its lower right position and reposition to the upper left corner. To resolve this issue, the created color palette has the same size as the source image, so no cropping occurs.

Text tiling

The last example tiles the text across the entire image, which makes removing the watermark even more difficult. Command line:

convert image.png  -font Arial -pointsize 20 \
    -draw "gravity south \
        fill black  text 0,12 'Copyright' \
        fill white  text 1,11 'Copyright'" \
    result.png

PHP Code:

<?php 
// 創(chuàng)建對象
$image = new Imagick('image.png');

// 水印文本
$text = 'Copyright';

// 創(chuàng)建新的繪圖面板
$draw = new ImagickDraw();

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('black');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在圖像上繪制文本
$image->annotateImage($draw, 10, 12, 0, $text);

// 稍微偏移位置，使用不同的顏色再次繪制文本
$draw->setFillColor('white');
$image->annotateImage($draw, 11, 11, 0, $text);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Reproduction picture:

Note that the transparency is set using setFillOpacity() here, instead of using an image mask.

Summary

For me, image processing in PHP has become one of the most enjoyable aspects of the language and I hope Imagick will be bundled together in future versions. If you are looking for ways to contribute, I encourage you to convert other command line examples to PHP and then post your results to the official PHP manual for others to learn and enjoy.

(Picture from Fotolia)

(The following is FAQ, the format and content have been adjusted according to the original text, and pseudo-original creations have been made)

Frequently Asked Questions about Adding Text Watermarks in PHP using Imagick (FAQ)

Q: How to add text watermark to an image using Imagick in PHP?

A: Using Imagick in PHP to add text watermarks to an image, you first need to create an instance of the Imagick class and read the image into it. Then, create an ImagickDraw instance and set the font properties. After that, you can use the annotateImage() method to add text to the image. Finally, use the writeImage() method to write the image to the file system. Here is a basic example:

convert -size 300x50 xc:grey30 -font Arial -pointsize 20 \
    -gravity center -draw "fill grey70  text 0,0  'Copyright'" \
    fgnd.png
convert -size 300x50 xc:black -font Arial -pointsize 20 -gravity center \
    -draw "fill white  text  1,1  'Copyright' \
        text  0,0  'Copyright' \
        fill black  text -1,-1 'Copyright'" \
    +matte mask.png
composite -compose CopyOpacity  mask.png  fgnd.png  stamp.png 
    mogrify -trim +repage stamp.png
composite -gravity south -geometry +0+10 stamp.png  image.png \
    result.png

Q: How to change the font color of watermark text in Imagick?

A: You can use the setFillColor() method of the ImagickDraw class to change the font color of the watermark text in Imagick. This method accepts strings representing colors. For example, to set the font color to red, you can do the following:

<?php
// 創(chuàng)建對象
$image = new Imagick('image.png');
$watermark = new Imagick();
$mask = new Imagick();
$draw = new ImagickDraw();

// 定義尺寸
$width = $image->getImageWidth();
$height = $image->getImageHeight();

// 創(chuàng)建調(diào)色板
$watermark->newImage($width, $height, new ImagickPixel('grey30'));
$mask->newImage($width, $height, new ImagickPixel('black'));

// 水印文本
$text = 'Copyright';

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('grey70');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在水印調(diào)色板上繪制文本
$watermark->annotateImage($draw, 10, 12, 0, $text);

// 在蒙版調(diào)色板上繪制文本
$draw->setFillColor('white');
$mask->annotateImage($draw, 11, 13, 0, $text);
$mask->annotateImage($draw, 10, 12, 0, $text);
$draw->setFillColor('black');
$mask->annotateImage($draw, 9, 11, 0, $text);

// 這是蒙版生效的必要條件
$mask->setImageMatte(false);

// 將蒙版應(yīng)用于水印
$watermark->compositeImage($mask, Imagick::COMPOSITE_COPYOPACITY, 0, 0);

// 將水印疊加到圖像上
$image->compositeImage($watermark, Imagick::COMPOSITE_DISSOLVE, 0, 0);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Q: How to change the font size of watermark text in Imagick?

A: You can use the setFontSize() method of the ImagickDraw class to change the font size of the watermark text in Imagick. This method accepts integers representing the font size. For example, to set the font size to 30, you can do the following:

convert image.png  -font Arial -pointsize 20 \
    -draw "gravity south \
        fill black  text 0,12 'Copyright' \
        fill white  text 1,11 'Copyright'" \
    result.png

Q: How to change the font of watermark text in Imagick?

A: You can use the setFont() method of the ImagickDraw class to change the font of the watermark text in Imagick. This method accepts strings representing the font name. For example, to set the font to "Arial", you can do the following:

<?php 
// 創(chuàng)建對象
$image = new Imagick('image.png');

// 水印文本
$text = 'Copyright';

// 創(chuàng)建新的繪圖面板
$draw = new ImagickDraw();

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('black');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在圖像上繪制文本
$image->annotateImage($draw, 10, 12, 0, $text);

// 稍微偏移位置，使用不同的顏色再次繪制文本
$draw->setFillColor('white');
$image->annotateImage($draw, 11, 11, 0, $text);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Q: How to locate watermark text in Imagick?

A: You can use the annotateImage() method of the Imagick class to set the position of the watermark text in Imagick. This method accepts four parameters: ImagickDraw instance, x and y coordinates of text, rotation angle of text, and text string. For example, to position text at coordinates (10, 45), you can do the following:

convert -size 300x50 xc:grey30 -font Arial -pointsize 20 \
    -gravity center -draw "fill grey70  text 0,0  'Copyright'" \
    fgnd.png
convert -size 300x50 xc:black -font Arial -pointsize 20 -gravity center \
    -draw "fill white  text  1,1  'Copyright' \
        text  0,0  'Copyright' \
        fill black  text -1,-1 'Copyright'" \
    +matte mask.png
composite -compose CopyOpacity  mask.png  fgnd.png  stamp.png 
    mogrify -trim +repage stamp.png
composite -gravity south -geometry +0+10 stamp.png  image.png \
    result.png

Q: How to rotate watermark text in Imagick?

A: You can use the annotateImage() method of the Imagick class to set the rotation angle of the watermark text in Imagick. The fourth parameter of this method is the rotation angle of the text. For example, to rotate the text by 45 degrees, you can do the following:

<?php
// 創(chuàng)建對象
$image = new Imagick('image.png');
$watermark = new Imagick();
$mask = new Imagick();
$draw = new ImagickDraw();

// 定義尺寸
$width = $image->getImageWidth();
$height = $image->getImageHeight();

// 創(chuàng)建調(diào)色板
$watermark->newImage($width, $height, new ImagickPixel('grey30'));
$mask->newImage($width, $height, new ImagickPixel('black'));

// 水印文本
$text = 'Copyright';

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFontSize(20);
$draw->setFillColor('grey70');

// 將文本定位在圖像的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在水印調(diào)色板上繪制文本
$watermark->annotateImage($draw, 10, 12, 0, $text);

// 在蒙版調(diào)色板上繪制文本
$draw->setFillColor('white');
$mask->annotateImage($draw, 11, 13, 0, $text);
$mask->annotateImage($draw, 10, 12, 0, $text);
$draw->setFillColor('black');
$mask->annotateImage($draw, 9, 11, 0, $text);

// 這是蒙版生效的必要條件
$mask->setImageMatte(false);

// 將蒙版應(yīng)用于水印
$watermark->compositeImage($mask, Imagick::COMPOSITE_COPYOPACITY, 0, 0);

// 將水印疊加到圖像上
$image->compositeImage($watermark, Imagick::COMPOSITE_DISSOLVE, 0, 0);

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Q: How to save watermarked images in Imagick?

A: You can use the writeImage() method of the Imagick class to save the watermark image. This method accepts a string representing the file path. For example, to save an image as "watermarked_image.png", you can do the following:

convert -size 140x80 xc:none -fill grey \
    -gravity NorthWest -draw "text 10,10 'Copyright'" \
    -gravity SouthEast -draw "text 5,15 'Copyright'" \
    miff:- | \
composite -tile - image.png  result.png

Q: How to add transparent watermark text to Imagick?

A: You can use the setFillOpacity() method of the ImagickDraw class to add transparent watermark text to Imagick. This method accepts floating point numbers representing the opacity level. For example, to set opacity to 0.5, you can do the following:

<?php
// 創(chuàng)建對象
$image = new Imagick('image.png');
$watermark = new Imagick();

// 水印文本
$text = 'Copyright';

// 創(chuàng)建新的繪圖面板
$draw = new ImagickDraw();
$watermark->newImage(140, 80, new ImagickPixel('none'));

// 設(shè)置字體屬性
$draw->setFont('Arial');
$draw->setFillColor('grey');
$draw->setFillOpacity(.5);

// 將文本定位在水印的左上角
$draw->setGravity(Imagick::GRAVITY_NORTHWEST);

// 在水印上繪制文本
$watermark->annotateImage($draw, 10, 10, 0, $text);

// 將文本定位在水印的右下角
$draw->setGravity(Imagick::GRAVITY_SOUTHEAST);

// 在水印上繪制文本
$watermark->annotateImage($draw, 5, 15, 0, $text);

// 重復(fù)將水印疊加到圖像上
for ($w = 0; $w < $image->getImageWidth(); $w += 140) {
    for ($h = 0; $h < $image->getImageHeight(); $h += 80) {
        $image->compositeImage($watermark, Imagick::COMPOSITE_OVER, $w, $h);
    }
}

// 設(shè)置輸出圖像格式
$image->setImageFormat('png');

// 輸出新圖像
header('Content-type: image/png');
echo $image;
?>

Q: How to add shadows to watermark text in Imagick?

A: You can add shadows to watermark text in Imagick by drawing the text twice (once for shadows, once for the text itself). Shadows can be created by setting the fill color to black and offsetting the text position. For example:

$imagick = new \Imagick(realpath('image.png'));
$draw = new \ImagickDraw();
$draw->setFillColor('white');
$draw->setFont('Arial');
$draw->setFontSize(50);
$imagick->annotateImage($draw, 10, 45, 0, 'Watermark Text');
$imagick->writeImage('watermarked_image.png');

Q: How to add watermark text to multiple images in Imagick?

A: To add watermark text to multiple images in Imagick, you can loop through the image and apply the watermark to each image. Here is a basic example:

$draw->setFillColor('red');

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