clip_hatch2.c

Clipping path demo program

This program create hatch pattern using lines, page transform (rotation) and clipping path.

Clipping path is created using HPDF_Page_Rectangle() function. In order to make clipping work properly, HPDF_Page_EndPath() function must be called right after HPDF_Page_Eoclip().

In this example clipping path is complex, constructed as intersections of two rectangles.

/*
 * << Haru Free PDF Library 2.4.4 >> -- minimal.c
 *
 * Copyright (c) 1999-2006 Takeshi Kanno <takeshi_kanno@est.hi-ho.ne.jp>
 * Copyright (c) 2023 Dmitry Solomennikov
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.
 * It is provided "as is" without express or implied warranty.
 *
 */
 
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <setjmp.h>
#include "hpdf.h"
#include "handler.h"
 
void
hatch (HPDF_Doc    pdf,
       HPDF_Page   page)
{
    HPDF_REAL height = HPDF_Page_GetHeight (page);
    HPDF_REAL width = HPDF_Page_GetWidth (page);
    HPDF_REAL x = 0.0;
 
    /* start clipping */
    HPDF_Page_GSave (page);
 
    /* prepare clipping path (rectangle with a hole) */
    HPDF_Page_Rectangle (page, 0, 0, width, 15 * HPDF_MM);
    HPDF_Page_Rectangle (page, 5*HPDF_MM, 5*HPDF_MM, width-10*HPDF_MM, 5 * HPDF_MM);
 
    /* use created path as clipping path (even-odd rule) */
    HPDF_Page_Eoclip (page);
 
    /* Finish path.
       This action instructs viewer that path is created and can be used as clipping path.
       It is required since it is possible to create complicated clipping path.
       For example, we can add another rectangle and its union will be used as clipping path.
       */
    HPDF_Page_EndPath (page);
 
    /* start hatch drawing */
    HPDF_Page_GSave (page);
 
    HPDF_Page_SetRGBStrokeHex (page, 0x55, 0x77, 0x22);
    HPDF_Page_SetLineWidth (page, 0.25 * HPDF_MM);
    HPDF_REAL angle1 = -45;
    HPDF_REAL rad1 = angle1 / 180 * HPDF_PI;
 
    /* rotate hatch */
    HPDF_Page_Concat (page, cos(rad1), sin(rad1), -sin(rad1), cos(rad1), -15*HPDF_MM, 0);
 
    while (x < width) {
        HPDF_Page_MoveTo (page, x, 0);
        HPDF_Page_LineTo (page, x, height);
        HPDF_Page_Stroke (page);
        x += HPDF_MM;
    }
 
    /* end of hatch drawing */
    HPDF_Page_GRestore (page);
 
    
 
    /* end of clipping */
    HPDF_Page_GRestore (page);
}
 
int
main (int argc, char **argv)
{
    HPDF_Doc  pdf;
    HPDF_Page page;
    char fname[256];
 
    strcpy (fname, argv[0]);
    strcat (fname, ".pdf");
 
    /* create document object*/
    pdf = HPDF_New (demo_error_handler, NULL);
    if (!pdf) {
        printf ("error: cannot create PdfDoc object\n");
        return 1;
    }
 
    if (setjmp(env)) {
        HPDF_Free (pdf);
        return 1;
    }
 
    /* add a new page object. */
    page = HPDF_AddPage (pdf);
 
    /* set up added page */
    HPDF_Page_SetSize (page, HPDF_PAGE_SIZE_A4, HPDF_PAGE_PORTRAIT);
 
    hatch (pdf, page);
 
    /* save document to a file */
    HPDF_SaveToFile (pdf, fname);
 
    /* clean up */
    HPDF_Free (pdf);
 
    return 0;
}