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<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><title>4.3. Truecolor Images</title><link rel="stylesheet" type="text/css" href="phplotdoc.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /><link rel="home" href="index.html" title="PHPlot Reference Manual" /><link rel="up" href="advanced.html" title="Chapter 4. PHPlot Advanced Topics" /><link rel="prev" href="adv-serialize.html" title="4.2. PHPlot Object Serialization" /><link rel="next" href="callbacks.html" title="4.4. Callbacks" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">4.3. Truecolor Images</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="adv-serialize.html">Prev</a> </td><th width="60%" align="center">Chapter 4. PHPlot Advanced Topics</th><td width="20%" align="right"> <a accesskey="n" href="callbacks.html">Next</a></td></tr></table><hr /></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="adv-truecolor"></a>4.3. Truecolor Images</h2></div></div></div><div class="abstract"><p class="title"><strong></strong></p><p>
3 
This section contains information about using
4 
<a class="link" href="concepts.html#def-truecolor">Truecolor images</a> in PHPlot.
5 
This material supplements the text in the <a class="xref" href="conc-colors.html" title="3.5. Colors">Section 3.5, &#8220;Colors&#8221;</a>.
6 
  </p></div><p>
7 
Truecolor image support was added to PHPlot-5.1.1. With Truecolor image
8 
support, you can:
9 
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Create images with a larger number of colors</p></li><li class="listitem"><p>Control color transparency with alpha blending</p></li><li class="listitem"><p>Perform advanced image processing operations</p></li></ul></div><p>
10 
</p><p>
11 
An example of using Truecolor with PHPlot can be found in
12 
<a class="xref" href="ex-truecolor-histogram.html" title="5.24. Example - Using Truecolor To Make a Histogram">Section 5.24, &#8220;Example - Using Truecolor To Make a Histogram&#8221;</a>.
13 
</p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-overview"></a>4.3.1. Using Truecolor Images in PHPlot</h3></div></div></div><p>
14 
To make a Truecolor image in PHPlot, create an object of the derived class
15 
<code class="literal">PHPlot_truecolor</code> instead of the class
16 
<code class="literal">PHPlot</code>.
17 
For example, replace this:
18 
</p><pre class="programlisting">$plot = new PHPlot(800, 600);
19 
</pre><p>
20 
with this:
21 
</p><pre class="programlisting">$plot = new PHPlot_truecolor(800, 600);
22 
</pre><p>
23 
</p><p>
24 
That is all you need to do in order to create truecolor images. All PHPlot
25 
methods are compatible with PHPlot_truecolor objects. An image file
26 
produced from a PHPlot_truecolor object with no other programming changes
27 
will be the same as an image file produced from a PHPlot object except as
28 
described under <a class="xref" href="adv-truecolor.html#adv-truecolor-fileformats" title="4.3.5. Image Formats and File Formats, Palette and Truecolor">Section 4.3.5, &#8220;Image Formats and File Formats, Palette and Truecolor&#8221;</a>.
29 
</p><p>
30 
One of the advantages of truecolor images is the ability to use
31 
variable transparency. This is described in the next two sections.
32 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-alpha"></a>4.3.2. Understanding Variable Transparency (Alpha)</h3></div></div></div><p>
33 
Colors in a truecolor image have four components: red, green, blue, and
34 
alpha. The alpha component corresponds to the transparency of a color.
35 
An alpha value of zero means the color is opaque, and an alpha value
36 
of 127 means the color is transparent, or clear.<a href="#ftn.idp1375167612" class="footnote" id="idp1375167612"><sup class="footnote">[4]</sup></a>
37 
In between values, from 1 to 126, correspond to various amounts of
38 
transparency.
39 
</p><p>
40 
Transparency is only meaningful when drawing objects on top of objects, or
41 
objects on top of the image background. An object drawn with an
42 
opaque color (alpha=0) will replace whatever was in the image before the
43 
object was drawn at that position. An object drawn with an transparent
44 
color (alpha=127) is invisible and does not affect the appearance of the
45 
image. An object drawn with a color that has an alpha value between 1 and
46 
126 will be combined with whatever was in the image before the object was
47 
drawn using alpha blending.
48 
</p><p>
49 
The PHP Manual explains alpha blending like this: "In blending mode, the
50 
alpha channel component of the color supplied to all drawing functions
51 
determines how much of the underlying color should be allowed to shine
52 
through. As a result, gd automatically blends the existing color at that
53 
point with the drawing color, and stores the result in the image. The
54 
resulting pixel is opaque."<a href="#ftn.idp1375104516" class="footnote" id="idp1375104516"><sup class="footnote">[5]</sup></a>
55 
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
56 
Note that the PHP Manual says the resulting pixel is opaque. This means
57 
that objects drawn with alpha above 0 are partially or completely transparent
58 
only relative to other objects in that same image. This does not result
59 
in an image with transparent portions which would show through to a browser
60 
or desktop background, for example.
61 
(Read the PHP Manual page for <code class="function">imagesavealpha</code> for more
62 
about this behavior and how to change it.)
63 
Use <a class="xref" href="SetTransparentColor.html" title="SetTransparentColor"><span class="refentrytitle">SetTransparentColor</span></a> to make portions of an image
64 
transparent to web page or desktop backgrounds.
65 
  </p></div><p>
66 
 
67 
The following figure shows the effect of alpha blending when drawing lines.
68 
The left side shows the normal overlaying of lines, and the right side
69 
shows alpha-blended overlaying of lines with alpha = 60 (that is, 60/127
70 
transparency).
71 
The effect of alpha blending can be seen where the data lines cross.
72 
Note: These plots use wide lines (3 pixels) and the portions of
73 
the images are magnified 2x to show detail.
74 
  </p><div class="informalfigure"><div class="mediaobject"><img src="images/alpha-blending.png" alt="Line intersections without and with alpha blending." /></div></div><p>
75 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-using-alpha"></a>4.3.3. Using Variable Transparency (Alpha) in PHPlot</h3></div></div></div><p>
76 
To use partially transparent colors (that is, colors with an alpha channel)
77 
with a PHPlot_truecolor object, you can specify an alpha value as part of a
78 
color specification, and you can specify a default alpha value for all data
79 
colors.
80 
</p><p>
81 
Use of alpha values with a color specification is described below,
82 
in <a class="xref" href="adv-truecolor.html#adv-truecolor-forms" title="4.3.4. Color Parameter Form Extensions">Section 4.3.4, &#8220;Color Parameter Form Extensions&#8221;</a>.
83 
Here are some examples of using colors with an alpha specification.
84 
</p><p>
85 
This sets the color used for labels to red=192, green=192, blue=33, and
86 
alpha=50 (that is, 50/127 transparency).
87 
</p><pre class="programlisting">$plot-&gt;SetTextColor(array(192, 192, 33, 50));
88 
</pre><p>
89 
</p><p>
90 
This sets the color used for tick marks to the color 'blue' from the color
91 
map, with alpha value 64 (64/127 transparency).
92 
</p><pre class="programlisting">$plot-&gt;SetTickColor('blue:64');
93 
</pre><p>
94 
</p><p>
95 
This sets colors for the first three data sets to red, green, and blue with
96 
different alpha values. The three colors are represented using
97 
different formats for illustration purposes.
98 
</p><pre class="programlisting">$plot-&gt;SetDataColors(array(
99 
      array(255, 0, 0, 60), // Red with alpha=60
100 
      '#00ff0050',          // Green with alpha=80 (0x50)
101 
      'blue:70'));          // Blue with alpha=70
102 
</pre><p>
103 
</p><p>
104 
Instead of specifying the alpha value for each data set color, you can
105 
provide a default alpha value for all data colors using the third argument to
106 
This uses the colors specified in $my_color_array with a default alpha of
107 
50. The default is applied to any color definition which does not already
108 
have an alpha value.
109 
<a class="xref" href="SetDataColors.html" title="SetDataColors"><span class="refentrytitle">SetDataColors</span></a>.
110 
</p><pre class="programlisting">$plot-&gt;SetDataColors($my_color_array, NULL, 50);
111 
</pre><p>
112 
</p><p>
113 
This can also be used to apply an alpha value to the default data colors.
114 
This retains the default data colors, but applies alpha = 50 (50/127
115 
transparency) to all the colors. This is a quick way to get partially
116 
transparent data colors without re-specifying all the colors.
117 
</p><pre class="programlisting">$plot-&gt;SetDataColors(NULL, NULL, 50);
118 
</pre><p>
119 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-forms"></a>4.3.4. Color Parameter Form Extensions</h3></div></div></div><p>
120 
In addition to the forms specified in <a class="xref" href="conc-colors.html#conc-colors-forms" title="3.5.1. Color Parameter Forms">Section 3.5.1, &#8220;Color Parameter Forms&#8221;</a>,
121 
colors specifications can include an alpha value. Although this works with
122 
palette images as well as truecolor images, specifying alpha values
123 
with palette images provides limited value.
124 
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
125 
A color name, as defined by <a class="xref" href="SetRGBArray.html" title="SetRGBArray"><span class="refentrytitle">SetRGBArray</span></a> or from a built-in
126 
color map if SetRGBArray was not called, followed by a colon and an alpha
127 
value as a decimal number, for example: 'red:60'. The alpha value is
128 
between 0 (opaque) and 127 (transparent).
129 
Note that colors in the color map can be defined with or without an alpha
130 
value. An alpha value appended to the color name overrides any specified
131 
in the color map. For example, if the color 'red2' is defined in the color
132 
map as array(255,0,0,80) - that is, red with 80/127 transparency - then
133 
'red2' has alpha of 80, and 'red2:40' has alpha of 40.
134 
    </p></li><li class="listitem"><p>
135 
Numeric color component values, in the form <code class="literal">#rrggbbaa</code>.
136 
Here rr is red, gg is green, and bb is blue, and each component
137 
value is represented as a 2-digit hexadecimal number between 00 and ff.
138 
Also aa is alpha, represented as a 2 digit hexadecimal number between 00 and 7f.
139 
For example, <code class="literal">#00ff0010</code> is green with 16/127 transparency.
140 
    </p></li><li class="listitem"><p>
141 
A PHP array of red, green, blue, and alpha color component values.
142 
Each value of red, green, and blue are in the range 0 to 255 inclusive,
143 
and the alpha component is in the range 0 to 127 inclusive.
144 
For example,
145 
<code class="literal">array(0,255,0,16)</code> is the same green with 16/127 transparency.
146 
    </p></li></ol></div><p>
147 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-fileformats"></a>4.3.5. Image Formats and File Formats, Palette and Truecolor</h3></div></div></div><p>
148 
PHPlot can produce JPEG, PNG, and GIF image files (and possibly others).
149 
You select the PHPlot output image file format with
150 
<a class="xref" href="SetFileFormat.html" title="SetFileFormat"><span class="refentrytitle">SetFileFormat</span></a>.
151 
</p><p>
152 
PHPlot works with GD images before producing an image file. There are two
153 
types of GD images: truecolor and palette. Truecolor images represent
154 
pixels as 32 bit values, combining 8 bits each of red, green, and blue
155 
components with a 7 bit alpha (transparency) value. Palette images use a
156 
color table with at most 256 entries, and represent pixels as 8 bit indexes
157 
into the color table. The palette image color table entries have 32 bit
158 
values, with the same components as truecolor image pixel values. So
159 
palette images in GD can have at most 256 unique colors, but there is no
160 
limitation on the number of unique colors in truecolor images.
161 
</p><p>
162 
As long as you don't specify a background image when creating your plot object,
163 
truecolor images are created with the <code class="literal">PHPlot_truecolor</code> class,
164 
and palette images are created with the <code class="literal">PHPlot</code> class.
165 
If you specify a background image, the GD image created by PHPlot matches the
166 
type - truecolor or palette - of your background image file.
167 
More on background image files can be found in
168 
<a class="xref" href="adv-truecolor.html#adv-truecolor-background" title="4.3.7. Background Images">Section 4.3.7, &#8220;Background Images&#8221;</a> below.
169 
</p><p>
170 
What happens when you output the GD image to an image file depends on the
171 
image file format you select.
172 
</p><p>
173 
JPEG image files are always truecolor. Whether you have a GD palette image
174 
or truecolor image, you will get a truecolor image file.  Note: You are
175 
discouraged from using JPEG images with PHPlot, because they are not
176 
optimal for this type of graphical information due to use of lossy
177 
compression.
178 
</p><p>
179 
GIF image files are always palette type, limited to 256 colors. If
180 
you have a GD palette image, you will get a palette GIF image file with the
181 
colors you used in your plot. If you have a a GD truecolor image, GD will
182 
convert your image to palette format, reducing the number of colors to 256
183 
if necessary. This may change the appearance of your plot. Note that some
184 
versions of the PHP manual for <code class="function">imagecreatetruecolor()</code>
185 
incorrectly state that you cannot output a GIF file from a truecolor GD image.
186 
</p><p>
187 
PNG image files support truecolor images and palette images of various
188 
color depths.  If you have a GD palette image, you will get a palette PNG
189 
image file. If you have a GD truecolor image, you will get a truecolor PNG
190 
image file. Note that by default, even though PNG truecolor image files
191 
support an alpha channel, GD eliminates the alpha channel when producing a
192 
PNG file. The visual effects of alpha blending are reproduced using opaque
193 
colors. GD apparently does this due to poor support in viewers for alpha
194 
channels. Refer to the PHP Manual page on
195 
<code class="function">imagesavealpha()</code> for details.
196 
</p><p>
197 
The following figure shows the relationship between constructor, background
198 
image format, GD image type, and image file format.
199 
  </p><div class="informalfigure"><div class="mediaobject"><img src="images/truecolor-formats.png" alt="Constrictor, GD image type, and image file formats." /></div></div><p>
200 
</p><p>
201 
In the initial release of Truecolor support in PHPlot-5.1.1, alpha channel
202 
information was ignored when using a PHPlot object, and only used with a
203 
PHPlot_truecolor object. This was changed in PHPlot-5.1.2, and alpha
204 
channel information is used for both PHPlot and PHPlot_truecolor classes.
205 
However, alpha channel information is not always useful with palette
206 
images.
207 
More on this can be found in <a class="xref" href="adv-truecolor.html#adv-truecolor-palette" title="4.3.9. Palette Images and Advanced Color Features">Section 4.3.9, &#8220;Palette Images and Advanced Color Features&#8221;</a> below.
208 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-plottypes"></a>4.3.6. Truecolor Images and Plot Types</h3></div></div></div><p>
209 
All PHPlot plot types work with truecolor images, but not all plot types
210 
work well with alpha blending of data colors.
211 
</p><p>
212 
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Pie Charts</span></dt><dd><p>
213 
Avoid using alpha blending with pie charts. The underlying GD
214 
routines do not fill the pie areas in a way that allows proper blending of
215 
colors. Flat pie charts (using SetShading(0)) are not too bad, showing some
216 
artifacts, but shaded or 3D-look pie charts are poorly rendered.
217 
      </p></dd><dt><span class="term">Bar Charts, </span><span class="term">Stacked Bar Charts</span></dt><dd><p>
218 
Bars are drawn properly, but the 3D shading affects get blended, resulting
219 
in less than ideal appearance. Flat, outlined bars (using SetShading(0))
220 
are fine with transparency, but when shading is on the 3D shadows overlap
221 
portions of the bars. With alpha blending, the overlaps take on new colors.
222 
      </p></dd></dl></div><p>
223 
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-background"></a>4.3.7. Background Images</h3></div></div></div><p>
224 
When creating a PHPlot or PHPlot_truecolor object, you can provide an
225 
existing image filename to the constructor as the fourth argument,
226 
<em class="parameter"><code>$input_file</code></em>.
227 
</p><pre class="programlisting">$plot = new PHPlot(800, 600, NULL, 'myimage.png');
228 
</pre><p>
229 
This image file becomes the background for your plot. (The function
230 
<a class="xref" href="dev-internal.html#SetInputFile">SetInputFile</a> also does this,
231 
but is deprecated for use except through the constructor.)
232 
</p><p>
233 
If you provide an input file to the constructor, the image associated with
234 
your PHPlot or PHPlot_truecolor object takes on the type of the input file:
235 
palette or truecolor. It does not matter which constructor you use when
236 
specifying an input file as background.
237 
(This was changed after the initial release of truecolor support.
238 
In PHPlot-5.1.1, you must use the PHPlot_truecolor constructor in order to
239 
use some truecolor features even when you use a truecolor background
240 
image file. Starting with PHPlot-5.1.2 you can use either constructor.)
241 
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
242 
The above applies only when an input file is specified to the PHPlot
243 
or PHPlot_truecolor constructor.  It does not apply to
244 
an image background set with <a class="xref" href="SetBgImage.html" title="SetBgImage"><span class="refentrytitle">SetBgImage</span></a>
245 
nor to a plot area background set with <a class="xref" href="SetPlotAreaBgImage.html" title="SetPlotAreaBgImage"><span class="refentrytitle">SetPlotAreaBgImage</span></a>.
246 
  </p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-callbacks"></a>4.3.8. Additional Operations on Truecolor Images Using Callbacks</h3></div></div></div><p>
247 
Advanced operations on truecolor PHPlot images are possible using PHPlot
248 
callbacks. See <a class="xref" href="callbacks.html" title="4.4. Callbacks">Section 4.4, &#8220;Callbacks&#8221;</a> for more information about using
249 
callbacks.  Here are some of the operations you can perform, and the
250 
corresponding GD functions.  Refer to the GD section of the PHP Manual for
251 
more information on these functions.
252 
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
253 
Some of these functions are only available when PHP was built with the
254 
bundled version of the GD library.
255 
  </p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="adv-truecolor-callbacks-antialias"></a>4.3.8.1. imageantialias()</h4></div></div></div><p>
256 
You can turn on anti-aliasing of truecolor images. This must be done before
257 
anything is drawn, so the pre-drawing callback <code class="literal">draw_setup</code>
258 
is used. Here is a partial example:
259 
</p><pre class="programlisting">function pre_plot($img)
260 
{
261 
    imageantialias($img, True);
262 
}
263 
...
264 
$plot = new PHPlot_truecolor(1024, 768);
265 
$plot-&gt;SetCallback('draw_setup', 'pre_plot');
266 
</pre><p>
267 
</p><p>
268 
Note: There are limitations with anti-aliased images. You cannot use wide
269 
lines (<a class="xref" href="SetLineWidths.html" title="SetLineWidths"><span class="refentrytitle">SetLineWidths</span></a>).
270 
Patterned lines do not work, so if you are displaying
271 
X or Y grid lines you must use <a class="xref" href="SetDrawDashedGrid.html" title="SetDrawDashedGrid"><span class="refentrytitle">SetDrawDashedGrid</span></a>(False)
272 
to make these solid.
273 
Also note that TrueType Font (TTF) text is always anti-aliased, even on
274 
palette images, regardless of the use of <code class="function">imageantialias()</code>.
275 
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="adv-truecolor-callbacks-alphablending"></a>4.3.8.2. imagealphablending() and imagelayereffect()</h4></div></div></div><p>
276 
These functions control the combining of partially transparent colors. They
277 
can be used via a <code class="literal">draw_setup</code> callback, in the same way
278 
as <code class="function">imageantialias</code> in the example above.
279 
Note that alpha blending is on by default with all truecolor images.
280 
</p></div><div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a id="adv-truecolor-callbacks-gammacorrect"></a>4.3.8.3. imagegammacorrect()</h4></div></div></div><p>
281 
You can have the GD library perform gamma adjustment on a truecolor image.
282 
This must be done after all drawing, so the post-drawing callback
283 
<code class="literal">draw_all</code> is used. Here is a partial example:
284 
</p><pre class="programlisting">function post_plot($img)
285 
{
286 
    imagegammacorrect($img, 1.0, 0.5); // Input gamma=1, output gamma=.5
287 
}
288 
 
289 
...
290 
$plot = new PHPlot_truecolor(1024, 768);
291 
$plot-&gt;SetCallback('draw_all', 'post_plot');
292 
</pre><p>
293 
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="adv-truecolor-palette"></a>4.3.9. Palette Images and Advanced Color Features</h3></div></div></div><p>
294 
You will have a GD palette image if you use the <code class="literal">PHPlot</code>
295 
constructor without a background image file, or if you use either the
296 
<code class="literal">PHPlot</code> or <code class="literal">PHPlot_truecolor</code>
297 
constructors with a background image file that is a palette image (GIF or
298 
some types of PNG). You can use alpha color specifications with palette GD
299 
images, but this is not recommended. The results are not well documented,
300 
but the following behavior has been observed:
301 
</p><p>
302 
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
303 
There is no alpha blending. Drawing operations simply replace existing
304 
pixels values with the new pixel values. (These are actually index values
305 
into the color table.)
306 
      </p></li><li class="listitem"><p>
307 
Alpha values are ignored when the image is output to a JPEG or GIF file.
308 
All colors are output as opaque.
309 
      </p></li><li class="listitem"><p>
310 
Alpha values are preserved in PNG image files. These will be palette, not
311 
truecolor, PNG images, with the color table containing the alpha values.
312 
You can therefore have palette PNG files with partial transparency, however
313 
not all viewers properly support this.
314 
      </p></li></ul></div><p>
315 
</p><p>
316 
Nothing described in <a class="xref" href="adv-truecolor.html#adv-truecolor-callbacks" title="4.3.8. Additional Operations on Truecolor Images Using Callbacks">Section 4.3.8, &#8220;Additional Operations on Truecolor Images Using Callbacks&#8221;</a> works with
317 
palette images, including gamma adjust and anti-aliasing (except that
318 
TrueType Font text is always anti-aliased.)
319 
</p></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idp1375167612" class="footnote"><p><a href="#idp1375167612" class="para"><sup class="para">[4] </sup></a>
320 
PHPlot follows the GD Library convention here. Other systems use alpha=0 to
321 
mean transparent, and a maximum alpha value to mean opaque.
322 
  </p></div><div id="ftn.idp1375104516" class="footnote"><p><a href="#idp1375104516" class="para"><sup class="para">[5] </sup></a>From the PHP Reference Manual,
323 
imagealphablending</p></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="adv-serialize.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="advanced.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="callbacks.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">4.2. PHPlot Object Serialization </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 4.4. Callbacks</td></tr></table></div></body></html>