imagettfbbox()

(PHP 4, PHP 5, PHP 7)

取得使用 TrueType 字体的文本的范围

说明

本函数计算并返回一个包围着 TrueType 文本范围的虚拟方框的像素大小。$size像素单位的字体大小。$angle$text将被度量的角度大小。$fontfile TrueType 字体文件的文件名（可以是 URL）。根据 PHP 所使用的 GD 库版本，可能尝试搜索那些不是以'/'开头的文件名并加上'.ttf'的后缀并搜索库定义的字体路径。$text要度量的字符串。imagettfbbox()返回一个含有 8 个单元的数组表示了文本外框的四个角：

本函数同时需要 GD 库和 FreeType 库。

参见imagettftext()。

I wrote a simple function that calculates the *exact* bounding box (single pixel precision).
The function returns an associative array with these keys:
left, top: coordinates you will pass to imagettftext 
width, height: dimension of the image you have to create 

As many of you know, this function is bugged in several versions of PHP. It should return the coordinates relative to the baseline of the font. So if your text includes characters like g and p then the bounding box should extend below zero on the Y axis, however it doesn't. This is a problem because imagettftext() positions text using the baseline, so all your text will be misaligned.
My solution is to create an image of the desired font and font-size using all ascii characters with imagettfbbox() and imagettftext(). The height of this image is used as the height for the real image.
I then analyse the image to get the vertical offset of the text (the background color should be $baseColor)

This offset can be used as the baseline for the font (for this font-size). You can use a similar trick for the horizontal offset, but that changes depending on the first character.

Please note that as imageTTFBbox and imageTTFText functions return an array of coordinates which could be negative numbers care must be taken with height and width calculations.
The rigth way to do that is to use the abs() function:
for an horizontal text:
$box = @imageTTFBbox($size,0,$font,$text);
$width = abs($box[4] - $box[0]);
$height = abs($box[5] - $box[1]);
Then to center your text at ($x,$y) position the code should be like that:
$x -= $width/2;
$y += $heigth/2;
imageTTFText($img,$size,0,$x,$y,$color,$font,$text);
this because (0,0) page origin is topleft page corner and (0,0) text origin is lower-left readable text corner.
Hope this help.

It seems to be worth pointing out that the "points" unit GD2 is using corresponds to 96 dpi, as defined in gd.h:
#define GD_RESOLUTION      96   /* pixels per inch */
So if you want to translate the bbox back to font points, you need to multiply all coordinates by 72/96 = 3/4.

Very CLEAR version of func., with example....

[ remember: No spaces before or after the  tag, because of header() call, you Roast! ]

This is a function which reformats a text string into a text block of a given width.
Usefull when you have a long single line string and want to fit it into a fixed width but don't care about it's height 

Here is a function that lets you write a string with your own "font tracking" level (the amount of pixels separating each character). It uses imagettfbbox to determine the width of each character, so it doesn't discriminate against the skinnier of characters. For this example, let $t = the amount of distance in pixels you want to separate each character from its neighbors.

Be aware that it currently does not work for angles other than the 0 default (I have no need for that).

Automatic line breaks: This simple function is able automatically create line breaks if you want to write a text on an image. All you have to specify is a maximum length. 

If you're looking for easy text alignment, you need to use the imagettfbbox() command. When given the correct parameters, it will return the boundaries of your to-be-made text field in an array, which will allow you to calculate the x and y coordinate that you need to use for centering or aligning your text.
A horizontal centering example:

$tb would contain:
Array
(
  [0] => 0 // lower left X coordinate
  [1] => -1 // lower left Y coordinate
  [2] => 198 // lower right X coordinate
  [3] => -1 // lower right Y coordinate
  [4] => 198 // upper right X coordinate
  [5] => -20 // upper right Y coordinate
  [6] => 0 // upper left X coordinate
  [7] => -20 // upper left Y coordinate
)
For horizontal alignment, we need to substract the "text box's" width { $tb[2] or $tb[4] } from the image's width and then substract by two.
Saying you have a 200px wide image, you could do something like this:

This'll give you perfect horizontal center alignment for your text, give or take 1 pixel. Have fun!

Please note that the 3rd argument is really a "path". 

use instead something like this:

or 

I have been testing this function for a while now and have come up with many of the same issues that other people have touched upon. Not being able to calculate the width of the text correctly. Or if a solution is found then it won't work with a hanging letter or a negative start letter like 'j'.
Like Ralph I also wanted to draw a box around some text and this would require me being pixel perfect with the font. The trouble is I did not know which font would be used or which size. This led me to come up with a solution which I am sharing below.

The function above gives the correct x and y coordinates that the text should be drawn from and also gives the actual image width and height. This has been tested with various fonts and sizes ranging from 6 up to 144 points. Some of the output will appear to be incorrect and have an extra pixel on the right, using verdana at size 144 and outputting the character 'Q' for example. This is not an error as this is part of the anti-aliasing of the font output.
Example Usage:

Return Values:
Array
(
  [0] => -8
  [1] => 40
  [2] => 715
  [3] => 40
  [4] => 715
  [5] => -177
  [6] => -8
  [7] => -177
  [x] => 6
  [width] => 722
  [y] => 176
  [height] => 216
)
Further notes can be found here along with images of the output of the function http://mikeleigh.com/links/imagettfbbox

measure bg image size, wrap text to fit image width 

For mixed text drawing on image, height given by this function is useless and leads to text's hip-hops over the baseline .
I will use just this: 

I found the bounding boxes a bit tricky to use when trying to rotate AND align text boxes. I wrote this function allows you to set left, right or center aligned text and also rotate it. 

Apparently the bounding box returned by imagettftext and imagettfbbox is not the same, and it appears as though imagettftext does a better job at calculating the actual bounding box (maybe because it has to render every character and it then finds out really everywhere it rendered).
So, you can create a dummy image render the text to it and get a better box. Here is an example function:

If you use this a lot, it would be better to keep one dummy image instead of continually creating and destroying images.

The returned array order is like this:
-----------------------------
| X:4 Y:5   | X:  Y:7    |
-----------------------------
| X:0 Y:1   | X:2 Y:3    |
-----------------------------
eg:
4 for the upper left X 
5 for the upper left Y and so on.

I found a simple solution that was working for me:
  
Here is the link with a examples:
http://www.tuxradar.com/practicalphp/11/2/6#null

It should be noted that the bounding box coordinates returned by this function are inaccurate - bug reports about this have been open for 5 years, so expect this will likely never be fixed. 
More information here:
https://gist.github.com/mindplay-dk/4429153

My solution to below-baseline characters is to simply apply a smaller angle and some padding when calculating your boundaries, so the function thinks your text goes below baseline. For example: 

SIMPLE OVERLOADED FUNCTION: Adds TTF Center and Right Alignment to co ordintate points.
Correctly demonstrates the use of the bouning box TTF function and the array of coordinates that it returns.
After obtaining values and adjusting based on a set of values [L, C, R], it uses simple math based of the length of the text to move it from the origin (x = 0 ) 

I was viewing the code for calculate the box of a text for a given font but I do not found one that works fine with different angles from zero, so I have made a function simpler than above:

With this function you can center an angled string in any image: 

I worked out a script that allows the transfer of alphanumeric data to be placed on an image. The HTML feature is img src and the php feature is imagettftext. This simple code will increment from 1 to 3 on images.
code:

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