Converts a class objects bitmap from any bits-per-pixel to any bits-per-pixel.


#include "ltwrappr.h"

virtual L_INT LBitmapBase::ColorRes(nBitsPerPixel, uFlags=CRF_FIXEDPALETTE|CRF_FLOYDSTEINDITHERING, pPalette=NULL, hPalette=NULL, uColors=0)

virtual L_INT LBitmapBase::ColorRes(BitmapSrc, nBitsPerPixel, uFlags=CRF_FIXEDPALETTE|CRF_FLOYDSTEINDITHERING, pPalette=NULL, hPalette=NULL, uColors=0)


L_INT nBitsPerPixel

The number of bits per pixel to increase or decrease the bitmap to. Valid values are 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 24, 32, 48, and 64.

L_UINT32 uFlags

Processing options. Note that the palette and dithering options are useful only when the resulting bitmap requires a palette (when it is 8 bits per pixel or less). You can combine values when appropriate by using a bitwise OR ( | ). Possible values are:

Value Meaning
CRF_FIXEDPALETTE [0x01] Use the fixed palette.
CRF_OPTIMIZEDPALETTE [0x02] Create an optimized palette, or if you supply a palette in the pPalette parameter, supply optimized colors for specified entries in the palette.
CRF_NETSCAPEPALETTE [0x40] Use the fixed palette that is employed by Netscape Navigator and by Microsoft Internet Explorer.
CRF_USERPALETTE [0x10] Use the palette specified in the pPalette parameter, without supplying optimized colors.
CRF_IDENTITYPALETTE [0x08] Insert the Windows system palette.
CRF_FASTMATCHPALETTE [0x20] Use a predefined table to speed conversion using your own palette. Refer to LBitmapSettings::CreateUserMatchTable.
CRF_BYTEORDERBGR [0x04] Use BGR color order. This flag only has meaning when going to 16 bits per pixel or higher.
CRF_BYTEORDERRGB [0x00] Use RGB color. This flag only has meaning when going to 16 bits per pixel or higher.
CRF_BYTEORDERGRAY [0x80] Grayscale.Destination bitmap should be 12, 16 or 32-bit grayscale. 12, 16 and 32-bit grayscale images are only supported in the Document/Medical toolkits.
CRF_SLOWMATCH [0x0200] Use with the CRF_OPTIMIZEDPALETTE flag to use a slower but more accurate matching process.
CRF_FAVORPURECOLORS [0x0400] Give colors that occur frequently in the image palette entries of their own in the optimized palette.
CRF_NODITHERING [0x00000000] Use nearest color matching.
CRF_FLOYDSTEINDITHERING [0x00010000] Use Floyd-Steinberg dithering.
CRF_STUCKIDITHERING [0x00020000] Use Stucki dithering.
CRF_BURKESDITHERING [0x00030000] Use Burkes dithering.
CRF_SIERRADITHERING [0x00040000] Use Sierra dithering.
CRF_STEVENSONARCEDITHERING [0x00050000] Use Stevenson Arce dithering.
CRF_JARVISDITHERING [0x00060000] Use Jarvis dithering.
CRF_ORDEREDDITHERING [0x00070000] Use ordered dithering, which is faster but less accurate than other dithering methods.
CRF_CLUSTEREDDITHERING [0x00080000] Use clustered dithering.
CRF_BYTEORDERROMM [0x0800] Use ROMM color. This flag only has meaning when going to 24 or 48 bits per pixel.
CRF_ALPHAINIT [0x01000000] Initialize the alpha channel for (32 or 64-bit color images) to all ones (0xFF for 8-bit alpha channels and 0xFFFF for 16-bit alpha channels). Without this flag, a created alpha channel initializes to zeros.
CRF_BYTEORDERRGB565 [0x00004000] RGB 565 byte order.


The custom palette to use. Specify this parameter as follows:


The custom palette to use. Specify this parameter as follows:

L_UINT uColors

The number of colors in the palette. Pass 0 to get the default (such as 256 for 8 bits per pixel). Otherwise, do one of the following:

LBitmapBase& BitmapSrc

The source bitmap on which the conversion will be done.


Value Meaning
SUCCESS The function was successful.
< 1 An error occurred. Refer to Return Codes.


Call this function to do a color resolution on the source class object's bitmap and place the result in the calling object's bitmap. Note that if the callback functions are enabled, then the LBitmapBase::ColorResBitmapCallBack function of the calling object will be called for the color resolution operation.

For general information about dithering, refer to Color Resolution and Dithering.

In specifying the output destination, you can convert the bitmap in place, create a new converted bitmap, or let your callback function handle the output.

In specifying a palette, you can use simple palette options, or you can specify a palette that is tailored to your needs. The tailored palette can be any size that you specify. It can include specific colors, reserved blank entries, and open entries that this function fills with optimized colors.

If you use the same tailored palette more than once, you can improve performance by creating a table, as explained in LBitmapSettings::CreateUserMatchTable.

Note: The BitmapSrc parameter is passed by reference, and is a required parameter.

NOTE: Using this function to change the color order of a 24-bit or 32-bit image (i.e. RGB to BGR) will have no effect on the image when painting or saving (to a file). If you want to change the visual appearance, you can simply swap the Order member of the BITMAPHANDLE.

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

This function supports stripping the alpha channel from the image.

Color Resolution Segment Function - Before

Color Resolution Segment Function - Before

Color Resolution Segment Function - After

Color Resolution Segment Function - After

View additional platform support for this Color Resolution Segment function.

Required DLLs and Libraries


Win32, x64.

See Also




This example is for LBitmapBase::ColorRes(BitmapSrc, nBitsPerPixel, uFlags, pPalette, hPalette, uColors):

L_INT LBitmapBase__ColorResExample() 
   L_INT nRet; 
   LBitmapBase MyBitmap,Bitmap2; 
   nRet =MyBitmap.Load(MAKE_IMAGE_PATH(TEXT("image1.cmp")),24); 
   if(nRet !=SUCCESS) 
      return nRet; 
   if(nRet !=SUCCESS) 
      return nRet; 
   return SUCCESS; 

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