PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Creating Images
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It takes as parameters the image identifier, the font, the x and y coordinates to start writing
the text, the text to write, and the color.
The font is a number between 1 and 5.These numbers represent a set of built-in
fonts in latin2 encoding, with higher numbers corresponding to larger fonts. As an alternative
to these fonts, you can use TrueType fonts or PostScript Type 1 fonts. Each of
these font sets has a corresponding function set.We use the TrueType functions in the
next example.
A good reason for using one of the alternative font function sets is that the text written
by imagestring() and associated functions, such as imagechar() (write a character
to the image) is aliased.The TrueType and PostScript functions produce antialiased text.
If you’re not sure what the difference is, look at Figure 22.2.Where curves or angled
lines appear in the letters, the aliased text appears jagged.The curve or angle is achieved
by using a “staircase” effect. In the antialiased image, when curves or angles appear in the
text, pixels in colors between the background and the text color are used to smooth the
text’s appearance.
Figure 22.2 Normal text appears jagged, especially in a large font size.
Antialiasing smoothes the curves and corners of the letters.
Outputting the Final Graphic
You can output an image either directly to the browser or to a file.
In this example, you output the image to the browser.This is a two-stage process.
First, you need to tell the web browser that you are outputting an image rather than text
or HTML.You do this by using the Header() function to specify the MIME type of the
image:
Header (‘Content-type: image/png’);
Normally, when you retrieve a file in your browser, the MIME type is the first thing the
web server sends. For an HTML or PHP page (post execution), the first thing sent is
Content-type: text/html
This tells the browser how to interpret the data that follows.
In this case, you want to tell the browser that you are sending an image instead of the
usual HTML output.You can do this by using the Header() function, which we have
not yet discussed.