Read the export settings, for a specified format, into a tree node.
bool tree_read_image_export_settings( TreeNode & trSettings, LPCSTR lpcszFormat )
true for success, false for error
//if we want to read the bmp(or jpg, etc..) image export setting, first you should
//export it: new a graphpage, then "File -> Export Graphs...", set "Image Type"
//as "Bitmap(*.bmp)" and change same setting you need and confirm. now, you can
//run the following code to read the export settings.
bool bRet = tree_read_image_export_settings(tr, "bmp");
if ( bRet )