The following figure is an example of how to create a custom fill pattern by using a hard-coded bit map. In this example, the bit map creates a pattern of arrows.

#define INCL_DOS
#define INCL_GPI
#define INCL_WIN
#include <os2.h>
   LONG lcidCustom;                  /* Bit map tag                           */
   HPS  hps;

   VOID CreatePattern(VOID);

   VOID MyFunction(VOID){
       CreatePattern();
       GpiSetPatternSet(hps, lcidCustom);
        .
        .
        .
   } /* func */

   VOID CreatePattern(VOID){
        HBITMAP hbm;               /* Bit map handle                          */
        BITMAPINFOHEADER2 bmp2;    /* Structure for bit map information       */
        PBITMAPINFO2 pbmi2;        /* Pointer to structure for bit map data   */
        PRGB2 prgb2;               /* Structure for color data                */
        ULONG cbBitmapInfo, cColors;

        BYTE abPattern[] = { 0xFF, 0xFF, 0xE7, 0xFF,
                             0xE7, 0xFF, 0xC3, 0xFF,
                             0xC3, 0xFF, 0x81, 0xFF,
                             0x81, 0xFF, 0xE7, 0xFF,
                             0xE7, 0xFF, 0xE7, 0xFF,
                             0xE7, 0xFF, 0xE7, 0xFF,
                             0xE7, 0xFF, 0xE7, 0xFF,
                             0xE7, 0xFF, 0xFF, 0xFF
   };


        lcidCustom = 1;            /* Bit map tag                             */

        bmp2.cbFix = (ULONG) sizeof(BITMAPINFOHEADER2);
        bmp2.cx = 8;               /* Bit map is 8 pels wide                  */
        bmp2.cy = 8;               /* Bit map is 8 pels high                  */
        bmp2.cPlanes = 1;          /* One bit plane                           */
        bmp2.cBitCount = 1;        /* One bit per pel                         */

        /* Use default values for the remainder of the structure.             */

        bmp2.ulCompression = 0;
        bmp2.cbImage = 0;
        bmp2.cxResolution = 0;
        bmp2.cyResolution = 0;
        bmp2.cclrUsed = 0;
        bmp2.cclrImportant = 0;
        bmp2.usUnits = 0;
        bmp2.usReserved = 0;
        bmp2.usRecording = 0;
        bmp2.usRendering = 0;
        bmp2.cSize1 = 0;
        bmp2.cSize2 = 0;
        bmp2.ulColorEncoding = 0;
        bmp2.ulIdentifier = 0;

        cColors = 1 << (bmp2.cBitCount * bmp2.cPlanes);

        cbBitmapInfo = sizeof(BITMAPINFO2) + (sizeof(RGB2) * cColors);

        DosAllocMem((PVOID)&pbmi2, cbBitmapInfo,
                    PAG_COMMIT | PAG_READ | PAG_WRITE);

        pbmi2->cbFix = bmp2.cbFix;
        pbmi2->cx = bmp2.cx;
        pbmi2->cy = bmp2.cy;
        pbmi2->cPlanes = bmp2.cPlanes;
        pbmi2->cBitCount = bmp2.cBitCount;

        /* Use default values for the remainder of the structure.             */

        pbmi2->ulCompression = 0;
        pbmi2->cbImage = 0;
        pbmi2->cxResolution = 0;
        pbmi2->cyResolution = 0;
        pbmi2->cclrUsed = 0;
        pbmi2->cclrImportant = 0;
        pbmi2->usUnits = 0;
        pbmi2->usReserved = 0;
        pbmi2->usRecording = 0;
        pbmi2->usRendering = 0;
        pbmi2->cSize1 = 0;
        pbmi2->cSize2 = 0;
        pbmi2->ulColorEncoding = 0;
        pbmi2->ulIdentifier = 0;

        prgb2 = (PRGB2) (pbmi2 + 1);  /* Set address to follow bmp2           */

        /* Set bit map colors to black and white.                             */
        prgb2[0].bBlue = 0;                               /* Color[0] = black */
        prgb2[0].bGreen = 0;                              /* Color[0] = black */
        prgb2[0].bRed = 0;                                /* Color[0] = black */
        prgb2[0].fcOptions = 0;
        prgb2[1].bBlue = 255;                             /* Color[1] = white */
        prgb2[1].bGreen = 255;                            /* Color[1] = white */
        prgb2[1].bRed = 255;                              /* Color[1] = white */
        prgb2[1].fcOptions = 0;

        /* Create a bit map and retrieve its handle.                          */
        hbm = GpiCreateBitmap(hps,
            &bmp2,
            CBM_INIT,
            (PBYTE) abPattern,                            /* Array of bits    */
            pbmi2);

        /* Tag the bit map just created with a custom identifier (lcid).      */
        GpiSetBitmapId(hps, hbm, lcidCustom);
   } /* CreatePattern */

Creating a Custom Fill Pattern from a Bit Map