Member

Description

uStructSize

Size of this structure, in bytes. Use the sizeof operator to calculate this value.

pBitmap

Pointer to the bitmap handle that references the bitmap used for preview or processing.

bZoomToFit

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)".

crTransparent

The color that will be transparent in the PNG image. This color is in RGB.

nPalType

Value that indicates the type of palette to use. Possible values are:

Value

Meaning

CRF_FIXEDPALETTE

Use the fixed palette.

CRF_OPTIMIZEDPALETTE

Create an optimized palette.

bAddWindowsColors

Flag that indicates whether to use the identity palette. Possible values are:

Value

Meaning

TRUE

Use the identity palette.

FALSE

Do not use the identity palette.

nDitherType

Flag that indicates the dithering type to use. Possible values are:

Value

Meaning

CRF_NODITHERING

Use nearest color matching

CRF_FLOYDSTEINDITHERING

Use Floyd-Steinberg dithering

CRF_STUCKIDITHERING

Use Stucki dithering

CRF_BURKESDITHERING

Use Burkes dithering

CRF_SIERRADITHERING

Use Sierra dithering

CRF_STEVENSONARCEDITHERING

Use Stevenson Arce dithering

CRF_JARVISDITHERING

Use Jarvis dithering

CRF_ORDEREDDITHERING

Use ordered dithering, which is faster but less accurate than other dithering methods.

CRF_CLUSTEREDDITHERING

Use clustered dithering

nBitsPerPixel

The bits per pixel for the tuned bitmap. Valid values are: 1, 4, 8, 24, and 32 bpp.

nNumOfColors

When nBitsPerPixel is 8 or less (the image is using indexed colors), this value represents the maximum number of colors that the PNG image can have. Possible values range from 2 to 256. Indexed PNG images can have from 2 colors to 256 colors. Using fewer colors results in smaller files, but also reduces the quality of the image.

nTransparencyTolerance

A tolerance value that determines how close a pixel's RGB value should be to the specified transparent color to be considered transparent. A tolerance of 0 means only the transparent color specified in crTransparent will be considered transparent. Specifying larger numbers will make more of the image transparent. Valid values are from 0 to 255.

bTransparent

Flag that indicates whether the PNG image will have a transparent color. Possible values are:

Value

Meaning

TRUE

The PNG image will have a transparent color.

FALSE

The PNG image will not have a transparent color.

Note: not all web browsers are capable of presenting transparency for PNG images (especially for 24bits PNG images).

uDlgFlags

User interface flags for this dialog which determines the layout and action of the dialog. This dialog doesn’t support the Auto-Process feature; however it makes up for that by allowing the user to export tuned images directly from the dialog. This is done by setting the DIALOG_PNGWEBTUNER_SHOW_EXPORT flag. Possible values are:

Value

Meaning

DLG_PNGWEBTUNER_SHOW_CONTEXTHELP

[0x00000001] Dialog should contain a context sensitive help icon.

DLG_PNGWEBTUNER_SHOW_PREVIEW

[0x00000002] Show a preview of the image in the dialog. The pBitmap member of this structure should contain a valid bitmap.

DLG_PNGWEBTUNER_SHOW_TOOL_ZOOMLEVEL

[0x00000004] Show the "Zoom to fit" and "Zoom Normal" toolbar buttons. The DLG_PNGWEBTUNER_SHOW_PREVIEW flag must be set in order to show these buttons.

DLG_PNGWEBTUNER_SHOW_TOOL_COLORPICKER

[0x00000008] Show the color button in the toolbar.

DLG_PNGWEBTUNER_SHOW_INFORMATION

[0x00000010] Show the Information group of controls.

DLG_PNGWEBTUNER_SHOW_ADDWINDOWCOLOR

[0x00000020] Show the Add Window Colors check box.

DLG_PNGWEBTUNER_SHOW_TRANSPARENCY

[0x00000040] Show the Transparency group of controls.

DLG_PNGWEBTUNER_SHOW_EXPORT

[0x00000080] Show the Export button instead of the OK button.

DLG_PNGWEBTUNER_SHOW_APPLY

[0x00000100] Show the Apply button in the dialog. The dialog will not apply any effect unless the user presses the Apply button.

pfnHelpCallback

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.

pHelpCallBackUserData

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 L_FAR *. 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.