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<title>Server Images</title>
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<h2 align="center">Server Images</h2>
<p>It is a high performance image compatible with a specific canvas. It is
faster than user image functions, but less flexible. It is commonly used for
off-screen drawing in Window Systems. </p>
<p>You can make gets and puts on several canvases but they must be created
using the same driver. It is possible to specify a part of the image to be
drawn, but it is not possible to zoom.</p>
<p>It is called "server" images because the data is stored in a system private
format, that the application (or the client) does not have access.</p>
<p>To create a server image there must be an active canvas of a driver with
server image support. Only the base drivers Win32, GDI+, X-Windows, XRender
and Cairo, support server images.</p>
<hr>
<pre class="function"><span class="mainFunction">cdImage* <a name="cdCreateImage">cdCanvasCreateImage</a>(cdCanvas* canvas, int w, int h); [in C]</span>
canvas:CreateImage(w, h: number) -> (image: cdImage) [in Lua]</pre>
<p>Creates a compatible image with size = <b><tt>w x h</tt></b> pixels. A
compatible image has the same color representation (number of bits per pixel)
of the active canvas. Once the server image is created it is independent of
the active canvas. The server image can only be used with an other canvas of
the same type as the canvas that was active when the image was created. The
default background is the same as the canvas, <strong><tt>CD_WHITE</tt></strong>.</p>
<pre class="function"><span class="mainFunction">void <a name="cdKillImage">cdKillImage</a>(cdImage* image); [in C]</span>
image:KillImage() [in Lua]</pre>
<p>Liberates memory allocated for the image. If this function is not called in
Lua, the garbage collector will call it.</p>
<pre class="function"><span class="mainFunction">void <a name="cdGetImage">cdCanvasGetImage</a>(cdCanvas* canvas, cdImage* image, int x, int y); [in C]</span>
canvas:GetImage(image: cdImage; x, y: number) [in Lua]</pre>
<p>Copies a rectangular region from the current rectangular context to the
memory <strong>(</strong><b><tt>image</tt></b><strong>)</strong>. <b><tt>(x,y)</tt></b>
is the coordinate of the bottom left corner of the rectangular region. The
width and length of the rectangular region are defined in the image structure
(when the image is created).</p>
<pre class="function"><span class="mainFunction">void <a name="cdPutImageRect">cdCanvasPutImageRect</a>(cdCanvas* canvas, cdImage* image, int x, int y, int xmin, int xmax, int ymin, int ymax); [in C]</span>
void wdCanvasPutImageRect(cdCanvas* canvas, cdImage* image, double x, double y, int xmin, int xmax, int ymin, int ymax); (WC) [in C]
canvas:PutImageRect(image: cdImage; x, y, xmin, xmax, ymin, ymax: number) [in Lua]
canvas:wPutImageRect(image: cdImage; x, y, xmin, xmax, ymin, ymax: number) (WC) [in Lua]</pre>
<p>Copies an image in a rectangular region of the canvas with the bottom left
corner in <tt><b>(x,y)</b></tt>. Allows specifying a rectangle inside the
image to be drawn, if <strong><font>xmin</font>,
<font>xmax</font>, <font>ymin</font> </strong>
and <strong><font>ymax</font></strong> are 0, then the whole
image is assumed.</p>
<pre class="function"><span class="mainFunction">void <a name="cdScrollArea">cdCanvasScrollArea</a>(cdCanvas* canvas, int xmin, int xmax, int ymin, int ymax, int dx, int dy); [in C]</span>
canvas:ScrollArea(xmin, xmax, ymin, ymax, dx, dy: number) [in Lua]</pre>
<p>Copies the rectangle defined by the coordinates <b><tt>(xmin,ymin)</tt></b>
and <b><tt>(xmax,ymax)</tt></b> to the rectangle defined by <b><tt>
(xmin+dx,ymin+dy)</tt></b> and <b><tt>(xmax+dx,ymax+dy)</tt></b>. It has the
same effect as <b><tt>cdGetImage</tt></b> followed by <tt><b>cdPutImage</b></tt>,
but it should be faster and does not require the explicit creation of an image
to be executed. Note that the region belonging to the first rectangle, but not
to the second, remains unchanged (the function does not clean this region).
</p>
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