How To: Use the IMAGESIZE tag of a GET_LAYOUT request
The IMAGESIZE tag of a GET_LAYOUT request consists of three attributes: dpi, width and height. IMAGESIZE affects the quality of the output. It also determines the size in pixels of image format output (bmp, jpg, png, or gif). Output in vector format (ai, emf, eps, pdf, or svg) is determined by the page size of the original ArcMap layout.
For more information please refer to the ArcXML Programmer's Reference Guide topic "Using GET_LAYOUT and LAYOUT with ArcMap Image Services".
The use of IMAGESIZE attributes depends on the output format being used.
For image format output (bmp, jpg, png, gif):
Width and height are required (the dpi setting will be ignored for image format output).
If no width and height are specified the following warning is printed into the log file: "Width and Height are not found in IMAGESIZE tag. Use default." The default is calculated based on the page size of the ArcMap layout and the default dpi of 96.
In order to maintain the proper map scale, width and height may be modified in order to maintain the aspect ratio present in the ArcMap layout.
For vector format output (ai, emf, eps, pdf, or svg):
DPI can be used to increase the quality of vector format output. If DPI is not specified in the IMAGESIZE tag the default value is used and the following warning is printed into the log file: "DPI is not found in IMAGESIZE tag. Use default."
The attributes width and height will be ignored. The size will be taken from the page size of the ArcMap layout.
When autoresize (an attribute of the GET_LAYOUT tag) is set to true and the layout with modified width and height is larger than the maximum image memory limit, the layout will be reduced to a size smaller than the Image Memory limit. The reduced image will also maintain the height/width ratio.