Use this function to initialize a new EVF. This is a required first step in defining a new EVF. This function returns a pointer to the new EVF file that you should use when adding vector records to the file (using ENVI_EVF_DEFINE_ADD_RECORD) and when completing the new file definition (using ENVI_EVF_DEFINE_CLOSE). The function allows you to specify an output filename, layer name, data type, and projection.

Note: The EVF pointer returned by this function is not the same as an ordinary EVF ID. When you create a new EVF, the EVF ID is returned only when the file definition is completed with the call to ENVI_EVF_DEFINE_CLOSE.

Syntax

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Result = ENVI_EVF_DEFINE_INIT(Filename [, DATA_TYPE={1 | 2 | 3 | 4 | 5 | 6 | 9 | 12 | 13 | 14 | 15}] [, LAYER_NAME=string] [, PROJECTION=structure])

Arguments

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Filename

This is a string that specifies an output filename for the EVF.

Keywords

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DATA_TYPE (optional)

Use this keyword to specify the ENVI Classic data type of the file. DATA_TYPE uses the following IDL convention. The default data type is double-precision if you do not set DATA_TYPE.

• 1: Byte (8 bits)
• 2: Integer (16 bits)
• 3: Long integer (32 bits)
• 4: Floating-point (32 bits)
• 5: Double-precision floating-point (64 bits)
• 6: Complex (2x32 bits)
• 9: Double-precision complex (2x64 bits)
• 12: Unsigned integer (16 bits)
• 13: Unsigned long integer (32 bits)
• 14: Long 64-bit integer
• 15: Unsigned long 64-bit integer

LAYER_NAME (optional)

Use this keyword to specify a single string name for the EVF layer. Each EVF consists of only a single layer. If you do not set LAYER_NAME, the default string is 'New Layer'.

PROJECTION (optional)

Use this keyword to specify a map projection. PROJECTION is a projection structure returned from ENVI_GET_PROJECTION or ENVI_PROJ_CREATE. The default projection is Arbitrary.

Example

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See the code example under ENVI_EVF_DEFINE_ADD_RECORD.

API Version

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4.2