Loading icons of a specific color depth

Hi,

Thanks for the comment, however, I'm not trying to circumvent this limitation, I'm looking for a way to load an icon image of a specific color depth, because even if LoadImage lets me specify the size I want to load, there's no API I know of which lets me specify the color depth.

p.s. Thanks for the LoadImage tip, I shall be careful about that.

Hi,

I found a solution myself. I have not tested it yet, but I'm pretty sure it should work.

I post it here so it might help other people who might have the same problem.

I've coded a LoadIconEx() function that allows specifying the color depth of the icon to be loaded

-- iconex.h --

#pragma pack( push )
#pragma pack( 2 )

typedef struct
{
   BYTE   bWidth;               // Width, in pixels, of the image
   BYTE   bHeight;              // Height, in pixels, of the image
   BYTE   bColorCount;          // Number of colors in image (0 if >=8bpp)
   BYTE   bReserved;            // Reserved
   WORD   wPlanes;              // Color Planes
   WORD   wBitCount;            // Bits per pixel
   DWORD  dwBytesInRes;         // how many bytes in this resource?
   WORD   nID;                  // the ID
} GRPICONDIRENTRY, *LPGRPICONDIRENTRY;

typedef struct
{
   WORD            idReserved;   // Reserved (must be 0)
   WORD            idType;       // Resource type (1 for icons)
   WORD            idCount;      // How many images?
   GRPICONDIRENTRY idEntries[1]; // The entries for each image
} GRPICONDIR, *LPGRPICONDIR;

#pragma pack( pop )

HICON LoadIconEx(HINSTANCE, LPCTSTR, int, int, int);

-- iconex.cpp --

#include <windows.h>

#include <math.h>   // For the pow() function

#include "iconex.h"

// LoadIconEx: Loads an icon with a specific size and color depth. This function
// will NOT try to strech or take an icon of another color depth if none is
// present.
HICON LoadIconEx(HINSTANCE hInstance, LPCTSTR lpszName, int cx, int cy, int uColors)
{
    HRSRC hRsrcIconGroup;

    // Load the icon group of the desired icon

    if (!(hRsrcIconGroup=FindResource(hInstance,lpszName,RT_GROUP_ICON)))
        return NULL;

    // Look for the specified color depth

    // Load the resource

    GRPICONDIR* pGrpIconDir;
    HRSRC hGlobalIconDir;

    if (!(hGlobalIconDir=LoadResource(hInstance,hRsrcIconGroup)))
        return NULL;

    // Lock the resource

    if (!(pGrpIconDir=(GRPICONDIR*) LockResource(hGlobalIconDir)))
        return NULL;

    // Cycle through all icon images trying to find the one we're looking for

    int i;
    BOOL bFound=FALSE;

    // In case of 8ppp or higher, the bColorCount of the structure is 0, and we
    // must find our icon with the wPlanes and wBitCount. So if the requested
    // number of colors is >=256, we calculate using those fields

    if (uColors>=256)
    {
        for (i=0;i<pGrpIconDir->idCount;i++)
        {
            // Color depth is always (bit count)*(plane count)
            // So color count is always (2^(color depth))
            if (uColors==pow(2,(pGrpIconDir->idEntries[i].wPlanes*
                     pGrpIconDir->idEntries[i].wBitCount)))
            {
                if ((pGrpIconDir->idEntries[i].bWidth==cx)&&
                    (pGrpIconDir->idEntries[i].bHeight==cy)) // Do the size match?
                {
                    bFound=TRUE;    // Yes, it matches
                    break;
                }
            }
        }
    }
    else
    {
        for (i=0;i<pGrpIconDir->idCount;i++)
        {
            if (pGrpIconDir->idEntries[i].bColorCount==uColors) // Do the color count match?
            {
                if ((pGrpIconDir->idEntries[i].bWidth==cx)&&
                    (pGrpIconDir->idEntries[i].bHeight==cy)) // Do the size match?
                {
                    bFound=TRUE;    // Yes, it matches
                    break;
                }
            }
        }
    }

    if (!bFound)
        return NULL;        // No icon was found matching the specs

    // Icon was found! i contains the index to the GRPICONDIR structure in the
    // icon group. Find the ID of the icon

    int nID;

    nID=pGrpIconDir->idEntries[i].nID;

    // Now, find the actual icon resource

    HRSRC hRsrcIcon;
    HRSRC hGlobalIcon;
    void* pIconBits;

    if (!(hRsrcIcon=FindResource(hInstance,MAKEINTRESOURCE(nID),RT_ICON)))
        return NULL;

    if (!(hGlobalIcon=LoadResource(hInstance,hRsrcIcon)))
        return NULL;

    if (!(pIconBits=LockResource(hGlobalIcon)))
        return NULL;

    // Now, use CreateIconFromResourceEx to create the actual HICON

    return CreateIconFromResourceEx(
        (unsigned char*) pIconBits, // Pointer to icon data
        pGrpIconDir->idEntries[i].dwBytesInRes, // Size of icon data
        TRUE, // TRUE to create an icon, not a cursor
        0x00030000, // Version number. MSDN says to put that number
        cx, cy, // Width and height
        0); // Flags (none)
}

-- end --

As for the points, DanRollins, even if your answer was not the one I was looking for, I liked a lot the links you've given me, so if you want them, just ask me, else I'll get them refunded.

Yes, I would like the points.  Thanks.
- Dan