Restricting the Range of an Input Image's Source17

These functions are only applicable when the input is a data reference, file, handle or pointer.

GraphicsExportSetInputOffsetAndLimit

Specifies the portion of an input data reference, file, handle or pointer that a graphics exporter is permitted to read. This would be useful if, for example, the source was a JPEG image embedded within a larger file.



 
pascal ComponentResult GraphicsExportSetInputOffsetAndLimit ( GraphicsExportComponent ci,

                                         unsigned long offset,

                                         unsigned long limit);

ci: Specifies the component instance that identifies your connection to the graphics exporter component.
offset: The byte offset of the input image data from the beginning of the data reference.
limit: The offset of the byte following the last byte of the input image data. (If you do not need to apply any limit, pass (unsigned long )-1.)

DISCUSSION

Both offset and limit are relative to the start of the compressed data. GraphicsExportGetInputDataSize and GraphicsExportReadInputData take the offset and limit into account automatically.

RESULT CODES

paramErr -50 limit < offset

GraphicsExportGetInputOffsetAndLimit

Retrieves the current input offset and limit.



 
pascal ComponentResult GraphicsExportGetInputOffsetAndLimit ( GraphicsExportComponent ci,

                                         unsigned long *offset,

                                         unsigned long *limit);

ci: Specifies the component instance that identifies your connection to the graphics exporter component.
offset: Points to a variable to receive the offset. If you do not need this information, pass nil .
limit: Points to a variable to receive the limit. If you do not need this information, pass nil .