transforms.c

Transformation helper functions

This program show usage of helper functions for coordinate system transformations. It creates transformation matrices for translate, scale, rotate and skew. For this purpose it uses HPDF_Page_Translate(), HPDF_Page_Scale(), HPDF_Page_Rotate() and HPDF_Page_Skew() respectively.

Internally all these functions use HPDF_Page_Concat() for transformation matrix manipulation.

/*
 * << Haru Free PDF Library 2.4.4 >> -- transforms.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 <setjmp.h>
#include "hpdf.h"
#include "handler.h"
 
const HPDF_REAL rect_height =  50*HPDF_MM;
const HPDF_REAL rect_width  =  50*HPDF_MM;
const HPDF_REAL line_width  = 0.2*HPDF_MM;
const HPDF_REAL font_size   = 14;
 
const char *captions[] = {
    "Translate",
    "Scale",
    "Rotate",
    "Skew",
    "Combined"
};
 
/* Draw original rectangle */
void draw_rect (HPDF_Page page)
{
    HPDF_Page_SetLineWidth (page, line_width);
    HPDF_Page_SetRGBStroke (page, 0, 0, 0);
    HPDF_Page_SetDash (page, NULL, 0, 0);
    HPDF_Page_Rectangle (page, 0, 0, rect_width, rect_height);
    HPDF_Page_Stroke (page);
}
 
/* Draw rectangle after transformation */
void draw_transformed (HPDF_Page page)
{
    HPDF_Page_SetLineWidth (page, line_width);
    HPDF_Page_SetRGBStroke (page, 1.0, 0, 1.0);
    const HPDF_REAL dash[] = {7};
    HPDF_Page_SetDash (page, dash, 1, 1);
    HPDF_Page_Rectangle (page, 0, 0, rect_width, rect_height);
    HPDF_Page_Stroke (page);
}
 
/* Draw transformation caption */
void draw_caption (HPDF_Page page, int index)
{
    HPDF_Page_BeginText (page);
    HPDF_Page_TextOut (page, 0, -1.5*font_size, captions[index]);
    HPDF_Page_EndText (page);
}
 
int
main (int argc, char **argv)
{
    HPDF_Doc  pdf;
    HPDF_Page page;
    HPDF_Font font;
    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_LANDSCAPE);
 
    /* create default-font */
    font = HPDF_GetFont (pdf, "Helvetica", NULL);
    HPDF_Page_SetFontAndSize (page, font, font_size);
 
    /* calculate rectangles positions */
    HPDF_REAL page_height = HPDF_Page_GetHeight (page);
 
    HPDF_REAL x[] = {20*HPDF_MM,
                     90*HPDF_MM,
                     20*HPDF_MM,
                     90*HPDF_MM,
                    160*HPDF_MM};
 
    HPDF_REAL y[] = {page_height - rect_height - 20*HPDF_MM,
                     page_height - rect_height - 20*HPDF_MM,
                     page_height - rect_height - 90*HPDF_MM,
                     page_height - rect_height - 90*HPDF_MM,
                     page_height - rect_height - 90*HPDF_MM};
 
    /* translate transformation */
    HPDF_Page_GSave (page);
 
    HPDF_Page_Translate (page, x[0], y[0]);
 
    HPDF_Page_GSave (page);
    draw_rect (page);
 
    HPDF_Page_Translate (page, 5*HPDF_MM, 5*HPDF_MM);
 
    draw_transformed (page);
    HPDF_Page_GRestore (page);
 
    draw_caption (page, 0);
 
    HPDF_Page_GRestore (page);
 
 
    /* scale transformation */
    HPDF_Page_GSave (page);
 
    HPDF_Page_Translate (page, x[1], y[1]);
 
    HPDF_Page_GSave (page);
    draw_rect (page);
 
    HPDF_Page_Scale (page, 0.8, 1.2);
 
    draw_transformed (page);
    HPDF_Page_GRestore (page);
 
    draw_caption (page, 1);
 
    HPDF_Page_GRestore (page);
 
    /* rotate transformation */
    HPDF_Page_GSave (page);
 
    HPDF_Page_Translate (page, x[2], y[2]);
 
    HPDF_Page_GSave (page);
    draw_rect (page);
 
    HPDF_Page_Rotate (page, HPDF_PI/20);
 
    draw_transformed (page);
    HPDF_Page_GRestore (page);
 
    draw_caption (page, 2);
 
    HPDF_Page_GRestore (page);
 
    /* skew transformation */
    HPDF_Page_GSave (page);
 
    HPDF_Page_Translate (page, x[3], y[3]);
 
    HPDF_Page_GSave (page);
    draw_rect (page);
 
    HPDF_Page_Skew (page, HPDF_PI/20, HPDF_PI/20);
 
    draw_transformed (page);
    HPDF_Page_GRestore (page);
 
    draw_caption (page, 3);
 
    HPDF_Page_GRestore (page);
 
    /* combined transformation */
    HPDF_Page_GSave (page);
 
    HPDF_Page_Translate (page, x[4], y[4]);
 
    HPDF_Page_GSave (page);
    draw_rect (page);
 
    HPDF_Page_Skew (page, HPDF_PI/20, HPDF_PI/20);
    HPDF_Page_Scale (page, 0.8, 1.2);
    HPDF_Page_Rotate (page, HPDF_PI/20);
    HPDF_Page_Translate (page, 5*HPDF_MM, 5*HPDF_MM);
 
    draw_transformed (page);
    HPDF_Page_GRestore (page);
 
    draw_caption (page, 4);
 
    HPDF_Page_GRestore (page);
 
    /* save document to a file */
    HPDF_SaveToFile (pdf, fname);
 
    /* clean up */
    HPDF_Free (pdf);
 
    return 0;
}