Almost every format filter in ImageGear has some attributes that it depends on while processing the Loadxxx and Savexxx methods of IGFormatsCtl Control. These attributes are called the control parameters of the filter. Your application can query these parameters, and change them to control the way that the filter operates. The ImageGear Supported File Formats Reference section in Chapter File Format Reference, where descriptions of filters are located, contains the full description of each control parameter for each format filter.

Your application accesses these control parameters using the GetParamCopy and GetParamCopyByIndex methods of IGFormatParams Object. Using these methods, your application gets IGControlParameter Object. If desired, your application can change the value in a given IGControlParameter Object, and then change the format filter behavior by calling UpdateParamFrom. To continue the preceding example, to tell the JPEG format filter to start saving a thumbnail image in any JPEG file, your application would execute the following:

Dim jpeg as IGFormatParams
.
. (set jpeg as above)
.
Dim param as IGControlParameter
Set param = jpeg.GetParamCopy("SAVE_THUMBNAIL")
param.Value.Boolean = True
jpeg.UpdateParamFrom param

In the case of TXT Filter to set the LINES_PER_PAGE and CHAR_PER_LINE control parameters, do not set the POINT_SIZE parameter because setting the PAGE_WIDTH, PAGE_HEIGHT and POINT_SIZE parameters provides sufficient page description, and LINES_PER_PAGE, CHAR_PER_LINE options are ignored. To set these parameters you should set POINT_SIZE option to zero.

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