One reason for using TTF fonts is the possibility to inserting unicode character/entities. With this we mean characters from the extended range that are not normally available on West european keyboards. This could for example be classical Greek characters often used in mathematics, for example the symbol for "pi". In order to make these and other commonly used "special" characters more accessible the library provides a utility class that makes it easy to use these characters without having to look up the corresponding unicode entities every time.

In order to specify characters not available on the keyboard the normal way is to specify there unicode code and included it in the text string with the prefix "&#". For example the unicode for the character "pi" is "03C0" in hex so to include this character in a text string you would have to write "This is pi π" note that the code should be given in decimal encoding in the string and always use 4 digits (pre-padded with 0:s as necessary). Since it is very tedious to lookup and encode special characters the library offers a simpler way. The SymChar class.

8.7.1. The utility class "SymChar"

As described above it is tedious to have to lookup all the character codes. To simplify this the SymChar class allows you to find these characters with the english common name of these symbols instead. For example to create a string with the Greek character "pi" one would have to write the code as shown in.

Example 8.2. Using the SymChar class to display the Greek letter "pi"

1 2 3 4 5 6

<?php // ... $pi = SymChar::Get('pi'); $graph->title->Set('Test is pi'.$pi); // ... ?>

All supported entities with there symbolic names are listed in Table 8.3. The first argument to the static method SymChar::Get() should be the name of the entity and if the second optional argument is true then the capital version (if it exists) of the symbol should be returned.

Table 8.3. Supported character entities in class SymChar

Name	Unicode	Unicode capital	Comment
"alpha"	03B1	0391	Greek character
"beta"	03B2	0392	Greek character
"gamma"	03B3	0393	Greek character
"delta"	03B4	0394	Greek character
"epsilon"	03B5	0395	Greek character
"zeta"	03B6	0396	Greek character
"ny"	03B7	0397	Greek character
"eta"	03B8	0398	Greek character
"theta"	03B8	0398	Greek character
"iota"	03B9	0399	Greek character
"kappa"	03BA	039A	Greek character
"lambda"	03BB	039B	Greek character
"mu"	03BC	039C	Greek character
"nu"	03BD	039D	Greek character
"xi"	03BE	039E	Greek character
"omicron"	03BF	039F	Greek character
"pi"	03C0	03A0	Greek character
"rho"	03C1	03A1	Greek character
"sigma"	03C3	03A3	Greek character
"tau"	03C4	03A4	Greek character
"upsilon"	03C5	03A5	Greek character
"phi"	03C6	03A6	Greek character
"chi"	03C7	03A7	Greek character
"psi"	03C8	03A8	Greek character
"omega"	03C9	03A9	Greek character
"euro"	20AC		Monetary symbol
"yen"	00A5		Monetary symbol
"pound"	20A4		Monetary symbol
"approx"	2248		Mathematical
"neq"	2260		Mathematical
"not"	2310		Mathematical
"def"	2261		Mathematical
"inf"	221E		Mathematical
"sqrt"	221A		Mathematical
"int"	222B		Mathematical
"copy"	00A9		Misc symbols
"para"	00A7		Misc symbols
"tm"	2122		Misc symbols
"rtm"	00AE		Misc symbols

Figure 8.6 and Figure 8.7 shows how these symbol look when they are rendered with the TTF font Times Roman 14pt. The symbols are in the same order as in the table above and are visually grouped by there category as specified in the column "Comment" in the table above.

Figure 8.6. Rendered symbol characters corresponding to

Figure 8.7. Rendered capital symbol characters corresponding to Table 8.3.

8.7.2. Graph example with Greek labels

In Figure 8.8 we have used the previous discussed SymChar class to more readily insert "π" characters in the X-axis label. We highlight some functionality that we haven't yet discussed in detail

1. We use a utility class (FuncGenerator available in "jpgraph_utils.inc.php") to help create plot values from a mathematical expression. This will help create a set of (x,y) points that can later on be used as the base for a data series.

2. The x-axis labels and the position of the tick marks on the x-axis are manually positioned and specified to be positioned at "even" fractions of π.

Figure 8.8. Specifying manual ticks as fraction of Pi. (manualtickex2.php)