Rendering a PDF or PS file with cairo
PDF files can be rendered to a cairo context using poppler. PS or EPS files can also be rendered to a cairo context by first converting to PDF using Ghostscript.
When using a vector backend, the vectors and text in the PDF file are preserved in the output as vectors. There is no unnecessary rasterization.
Compile the examples with:
gcc -o pdftops pdftops.c `pkg-config --cflags --libs cairo poppler-glib`
gcc -o pdftoimage pdftoimage.c `pkg-config --cflags --libs cairo poppler-glib`
pdftops.c - Render a PDF file to a cairo PostScript surface.
#include <poppler.h>
#include <cairo.h>
#include <cairo-ps.h>
int main(int argc, char *argv[])
{
PopplerDocument *document;
PopplerPage *page;
double width, height;
GError *error;
const char *filename;
gchar *absolute, *uri;
int num_pages, i;
cairo_surface_t *surface;
cairo_t *cr;
cairo_status_t status;
if (argc != 2) {
printf ("Usage: pdf2cairo input_file.pdf\n");
return 0;
}
filename = argv[1];
g_type_init ();
error = NULL;
if (g_path_is_absolute(filename)) {
absolute = g_strdup (filename);
} else {
gchar *dir = g_get_current_dir ();
absolute = g_build_filename (dir, filename, (gchar *) 0);
free (dir);
}
uri = g_filename_to_uri (absolute, NULL, &error);
free (absolute);
if (uri == NULL) {
printf("poppler fail: %s\n", error->message);
return 1;
}
document = poppler_document_new_from_file (uri, NULL, &error);
if (document == NULL) {
printf("poppler fail: %s\n", error->message);
return 1;
}
num_pages = poppler_document_get_n_pages (document);
/* Page size does not matter here as the size is changed before
* each page */
surface = cairo_ps_surface_create ("output.ps", 595, 842);
cr = cairo_create (surface);
for (i = 0; i < num_pages; i++) {
page = poppler_document_get_page (document, i);
if (page == NULL) {
printf("poppler fail: page not found\n");
return 1;
}
poppler_page_get_size (page, &width, &height);
cairo_ps_surface_set_size (surface, width, height);
cairo_save (cr);
poppler_page_render_for_printing (page, cr);
cairo_restore (cr);
cairo_surface_show_page (surface);
g_object_unref (page);
}
status = cairo_status(cr);
if (status)
printf("%s\n", cairo_status_to_string (status));
cairo_destroy (cr);
cairo_surface_finish (surface);
status = cairo_surface_status(surface);
if (status)
printf("%s\n", cairo_status_to_string (status));
cairo_surface_destroy (surface);
g_object_unref (document);
return 0;
}
pdftoimage.c - Render a one page of a PDF file to a cairo image surface.
#include <stdio.h>
#include <stdlib.h>
#include <poppler.h>
#include <cairo.h>
#define IMAGE_DPI 150
int main(int argc, char *argv[])
{
PopplerDocument *document;
PopplerPage *page;
double width, height;
GError *error;
const char *pdf_file;
const char *png_file;
gchar *absolute, *uri;
int page_num, num_pages;
cairo_surface_t *surface;
cairo_t *cr;
cairo_status_t status;
if (argc != 4) {
printf ("Usage: pdftoimage input_file.pdf output_file.png page\n");
return 0;
}
pdf_file = argv[1];
png_file = argv[2];
page_num = atoi(argv[3]);
g_type_init ();
error = NULL;
if (g_path_is_absolute(pdf_file)) {
absolute = g_strdup (pdf_file);
} else {
gchar *dir = g_get_current_dir ();
absolute = g_build_filename (dir, pdf_file, (gchar *) 0);
free (dir);
}
uri = g_filename_to_uri (absolute, NULL, &error);
free (absolute);
if (uri == NULL) {
printf("%s\n", error->message);
return 1;
}
document = poppler_document_new_from_file (uri, NULL, &error);
if (document == NULL) {
printf("%s\n", error->message);
return 1;
}
num_pages = poppler_document_get_n_pages (document);
if (page_num < 1 || page_num > num_pages) {
printf("page must be between 1 and %d\n", num_pages);
return 1;
}
page = poppler_document_get_page (document, page_num - 1);
if (page == NULL) {
printf("poppler fail: page not found\n");
return 1;
}
poppler_page_get_size (page, &width, &height);
/* For correct rendering of PDF, the PDF is first rendered to a
* transparent image (all alpha = 0). */
surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
IMAGE_DPI*width/72.0,
IMAGE_DPI*height/72.0);
cr = cairo_create (surface);
cairo_scale (cr, IMAGE_DPI/72.0, IMAGE_DPI/72.0);
cairo_save (cr);
poppler_page_render (page, cr);
cairo_restore (cr);
g_object_unref (page);
/* Then the image is painted on top of a white "page". Instead of
* creating a second image, painting it white, then painting the
* PDF image over it we can use the CAIRO_OPERATOR_DEST_OVER
* operator to achieve the same effect with the one image. */
cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OVER);
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
status = cairo_status(cr);
if (status)
printf("%s\n", cairo_status_to_string (status));
cairo_destroy (cr);
status = cairo_surface_write_to_png (surface, png_file);
if (status)
printf("%s\n", cairo_status_to_string (status));
cairo_surface_destroy (surface);
g_object_unref (document);
return 0;
}