References ▼
The PREWITTFILTERDLGPARAMS structure provides information used to initialize the dialog box created by the L_DlgPrewittFilter function. After the user closes the dialog box, this structure is updated with information about the user's selections.
typedef struct _PREWITTFILTERDLGPARAMS{L_UINT uStructSize;pBITMAPHANDLE pBitmap;L_BOOL bZoomToFit;pSPATIALFLT pFilter;L_UINT32 uDlgFlags;LTCOMMDLGHELPCB pfnHelpCallback;L_VOID *pHelpCallBackUserData;} PREWITTFILTERDLGPARAMS,* LPPREWITTFILTERDLGPARAMS;
Size of this structure, in bytes. Use the sizeof operator to calculate this value.
Pointer to the bitmap handle that references the bitmap used for preview or processing.
Flag that indicates the initial zoom level for previewing the image. Possible values are:
| Value | Meaning |
|---|---|
| TRUE | Set the initial zoom level to "Zoom to fit". |
| FALSE | Set the initial zoom level to "Normal (1:1)". |
Address of a variable to be updated with the spatial filter selected in the dialog. The Prewitt filter applies Prewitt edge detection. All pixels not on the detected edges are changed to black. (The usage is the same as Sobel, but the algorithm is different.) Choose the appropriate value for horizontal or vertical detection. Possible values are:
User interface flags for this dialog, which determine the layout and action of the dialog. Possible values are:
| Value | Meaning |
|---|---|
| DLG_PREWITTFILTER_AUTOPROCESS | [0x00000001] process the image on OK. The pBitmap member of this structure should contain a valid bitmap. |
| DLG_PREWITTFILTER_SHOW_CONTEXTHELP | [0x00000002] dialog should contain a context sensitive help icon. |
| DLG_PREWITTFILTER_SHOW_PREVIEW | [0x00000004] show a preview of the image in the dialog. The pBitmap member of this structure should contain a valid bitmap. |
| DLG_PREWITTFILTER_SHOW_TOOL_ZOOMLEVEL | [0x00000008] show the "Zoom to fit" and "Zoom Normal" toolbar buttons. The DLG_PREWITTFILTER_SHOW_PREVIEW flag must be set in order to show these buttons. |
Pointer to an optional help callback function. If you do not wish to provide help to this dialog, use NULL as the value of this parameter. To provide help to this dialog, use the function pointer as the value of this parameter. The callback function must adhere to the prototype described in LTCOMMDLGHELPCB.
Void pointer that you can use to pass one or more additional parameters that the callback function needs. To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pHelpCallBackUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure. If the additional parameters are not needed, you can pass NULL in this parameter.