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## 6.5 How does StrokeCSIM() work?

Knowledge of the exact technical details of the way StrokeCSIM() works is probably not needed by many people but for completeness we outline those details in this short section.

The fundamental issue we have to solve is that we must be able to call the image script in two modes. When the user includes the image script the StrokeCSIM() method should return the HTML page but when the image script is later called directly in the image tag it must not return an HTML page but rather the actual image.

The way this is solved is by using one HTTP argument which is passed on automatically when we use the image script name in the image-tag.

If you look at the generated HTML you will see that the argument to the src-property of the image tag is not simply the script name but the script name with a additional argument.

In the JpGraph internal code this pre-defined argument is checked for and if it exists the image is send back and not the HTML page.

The name of this argument is defined by a DEFINE() statement in JpGraph. The define is _CSIM_DISPLAY.

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