Jython
 
 

Download sprites used in the following examples

Image manipulation has become a frequent occupation for many people due to the wide-spread of digital cameras. Despite picture manipulation is normally performed using professional applications (like Photoshop), a basic understanding that a digital picture consists of a rectangular array of "color points" (called pixels) that are coded by integers is essential. The RGB color model uses 8 bits (numbers from 0 to 255) for each of the three colors RED, GREEN and BLUE that defines the intensity of a red, green and blue light emitting point.

Because from the intuitive understanding it is not evident that pictures are coded by integers, programming using images provides a profound insight about computer generated images. Implementing some simple imaging algorithms in Python broadens the understanding of how imaging software works and gives a good motivation for programming courses.

There are many imaging libraries available. In Python professional programmers often use the Python Imaging Library (PIL) that is very extensive, offering a wide range of facilities.

In introductory programming courses, PIL may be an overkill and a simpler imaging API will do. The GPanel class provides a simple graphics playground based on a user definable double coordinates with mouse support. Based on the underlying Java classes it was easy to add some simple image management functions that fit neatly into the GPanel API. Here we present some demonstrations of how to use them.

In the first example an image is loaded from a image file and shown as original and zoomed by a factor of 2 and rotated 60 degrees.

Error Page

Error Page

Stack trace:

java.io.FileNotFoundException: The requested resource [/home/pyincludes/ImageEx1.html] is not available
	at org.apache.catalina.servlets.DefaultServlet.serveResource(DefaultServlet.java:845)
	at org.apache.catalina.servlets.DefaultServlet.doGet(DefaultServlet.java:497)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	at org.apache.catalina.servlets.DefaultServlet.service(DefaultServlet.java:477)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.jython_005fex8_jsp._jspService(jython_005fex8_jsp.java:162)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.printcenter_jsp._jspService(printcenter_jsp.java:157)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at sun.reflect.GeneratedMethodAccessor64.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:253)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:191)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:432)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

Request URL:

http://www.aplu.ch/home/printcenter.jsp

Parameters:

    center_to_include: jython_ex8.jsp