Update docs/example.c to use utility functions.

And add error handling.

1 files changed, 122 insertions, 109 deletions

diff --git a/docs/example.c b/docs/example.c
index 257e17f9..3099ecb1 100644
--- a/docs/example.c
+++ b/docs/example.c
@@ -1,120 +1,133 @@
-// Rendering a page of a PDF document to a PNG image in less than 100 lines.
-
-// Compile a debug build of mupdf, then compile and run this example:
-//
-// gcc -g -o build/debug/example -Iinclude docs/example.c \
-//	build/debug/libmupdf.a \
-//	build/debug/libfreetype.a build/debug/libjbig2dec.a \
-//	build/debug/libjpeg.a build/debug/libopenjpeg.a \
-//	build/debug/libmujs.a \
-//	build/debug/libz.a -lm
-//
-// (If this fails with errors about missing BIO_ and X509_ references
-// try again with "-lcrypto" added to the end of that command).
-//
-// build/debug/example /path/to/document.pdf 1 200 25
-
-// Include the MuPDF header file.
+/*
+	How to use MuPDF to render a single page and print the result as a PPM to stdout.
+
+	Build the mupdf library using make, then either run 'make examples' or
+	compile the example manually:
+
+	gcc -Iinclude -o example.exe docs/example.c build/debug/libmupdf.a \
+		build/debug/libfreetype.a \
+		build/debug/libjbig2dec.a \
+		build/debug/libjpeg.a \
+		build/debug/libmujs.a \
+		build/debug/libopenjpeg.a \
+		build/debug/libz.a \
+		-lcrypto \
+		-lm
+
+	./example.exe document.pdf 100 0 1
+*/
+
 #include <mupdf/fitz.h>
 
-void
-render(char *filename, int pagenumber, int zoom, int rotation)
+int main(int argc, char **argv)
 {
+	char *input;
+	float zoom, rotate;
+	int page_number, page_count;
 	fz_context *ctx;
 	fz_document *doc;
-	int pagecount;
-	fz_page *page;
-	fz_matrix transform;
-	fz_rect bounds;
-	fz_irect bbox;
 	fz_pixmap *pix;
-	fz_device *dev;
-
-	// Create a context to hold the exception stack and various caches.
-
+	fz_matrix ctm;
+	int x, y;
+
+	if (argc < 3)
+	{
+		fprintf(stderr, "usage: example input-file page-number [ zoom [ rotate ] ]\n");
+		fprintf(stderr, "\tinput-file: path of PDF, XPS, CBZ or EPUB document to open\n");
+		fprintf(stderr, "\tPage numbering starts from one.\n");
+		fprintf(stderr, "\tZoom level is in percent (100 percent is 72 dpi).\n");
+		fprintf(stderr, "\tRotation is in degrees clockwise.\n");
+		return EXIT_FAILURE;
+	}
+
+	input = argv[1];
+	page_number = atoi(argv[2]) - 1;
+	zoom = argc > 3 ? atof(argv[3]) : 100;
+	rotate = argc > 4 ? atof(argv[4]) : 0;
+
+	/* Create a context to hold the exception stack and various caches. */
 	ctx = fz_new_context(NULL, NULL, FZ_STORE_UNLIMITED);
-
-	// Register the default file types.
-
-	fz_register_document_handlers(ctx);
-
-	// Open the PDF, XPS or CBZ document.
-
-	doc = fz_open_document(ctx, filename);
-
-	// Retrieve the number of pages (not used in this example).
-
-	pagecount = fz_count_pages(ctx, doc);
-
-	// Load the page we want. Page numbering starts from zero.
-
-	page = fz_load_page(ctx, doc, pagenumber - 1);
-
-	// Calculate a transform to use when rendering. This transform
-	// contains the scale and rotation. Convert zoom percentage to a
-	// scaling factor. Without scaling the resolution is 72 dpi.
-
-	fz_rotate(&transform, rotation);
-	fz_pre_scale(&transform, zoom / 100.0f, zoom / 100.0f);
-
-	// Take the page bounds and transform them by the same matrix that
-	// we will use to render the page.
-
-	fz_bound_page(ctx, page, &bounds);
-	fz_transform_rect(&bounds, &transform);
-
-	// Create a blank pixmap to hold the result of rendering. The
-	// pixmap bounds used here are the same as the transformed page
-	// bounds, so it will contain the entire page. The page coordinate
-	// space has the origin at the top left corner and the x axis
-	// extends to the right and the y axis extends down.
-
-	fz_round_rect(&bbox, &bounds);
-	pix = fz_new_pixmap_with_bbox(ctx, fz_device_rgb(ctx), &bbox);
-	fz_clear_pixmap_with_value(ctx, pix, 0xff);
-
-	// A page consists of a series of objects (text, line art, images,
-	// gradients). These objects are passed to a device when the
-	// interpreter runs the page. There are several devices, used for
-	// different purposes:
-	//
-	//	draw device -- renders objects to a target pixmap.
-	//
-	//	text device -- extracts the text in reading order with styling
-	//	information. This text can be used to provide text search.
-	//
-	//	list device -- records the graphic objects in a list that can
-	//	be played back through another device. This is useful if you
-	//	need to run the same page through multiple devices, without
-	//	the overhead of parsing the page each time.
-
-	// Create a draw device with the pixmap as its target.
-	// Run the page with the transform.
-
-	dev = fz_new_draw_device(ctx, pix);
-	fz_run_page(ctx, page, dev, &transform, NULL);
-	fz_drop_device(ctx, dev);
-
-	// Save the pixmap to a file.
-
-	fz_write_png(ctx, pix, "out.png", 0);
-
-	// Clean up.
-
+	if (!ctx)
+	{
+		fprintf(stderr, "cannot create mupdf context\n");
+		return EXIT_FAILURE;
+	}
+
+	/* Register the default file types to handle. */
+	fz_try(ctx)
+		fz_register_document_handlers(ctx);
+	fz_catch(ctx)
+	{
+		fprintf(stderr, "cannot register document handlers: %s\n", fz_caught_message(ctx));
+		fz_drop_context(ctx);
+		return EXIT_FAILURE;
+	}
+
+	/* Open the document. */
+	fz_try(ctx)
+		doc = fz_open_document(ctx, input);
+	fz_catch(ctx)
+	{
+		fprintf(stderr, "cannot open document: %s\n", fz_caught_message(ctx));
+		fz_drop_context(ctx);
+		return EXIT_FAILURE;
+	}
+
+	/* Count the number of pages. */
+	fz_try(ctx)
+		page_count = fz_count_pages(ctx, doc);
+	fz_catch(ctx)
+	{
+		fprintf(stderr, "cannot count number of pages: %s\n", fz_caught_message(ctx));
+		fz_drop_document(ctx, doc);
+		fz_drop_context(ctx);
+		return EXIT_FAILURE;
+	}
+
+	if (page_number < 0 || page_number >= page_count)
+	{
+		fprintf(stderr, "page number out of range: %d (page count %d)\n", page_number + 1, page_count);
+		fz_drop_document(ctx, doc);
+		fz_drop_context(ctx);
+		return EXIT_FAILURE;
+	}
+
+	/* Compute a transformation matrix for the zoom and rotation desired. */
+	/* The default resolution without scaling is 72 dpi. */
+	fz_scale(&ctm, zoom / 100, zoom / 100);
+	fz_pre_rotate(&ctm, rotate);
+
+	/* Render page to an RGB pixmap. */
+	fz_try(ctx)
+		pix = fz_new_pixmap_from_page_number(ctx, doc, page_number, &ctm, fz_device_rgb(ctx));
+	fz_catch(ctx)
+	{
+		fprintf(stderr, "cannot render page: %s\n", fz_caught_message(ctx));
+		fz_drop_document(ctx, doc);
+		fz_drop_context(ctx);
+		return EXIT_FAILURE;
+	}
+
+	/* Print image data in ascii PPM format. */
+	printf("P3\n");
+	printf("%d %d\n", pix->w, pix->h);
+	printf("255\n");
+	for (y = 0; y < pix->h; ++y)
+	{
+		unsigned char *p = &pix->samples[y * pix->w * pix->n];
+		for (x = 0; x < pix->w; ++x)
+		{
+			if (x > 0)
+				printf("  ");
+			printf("%3d %3d %3d", p[0], p[1], p[2]);
+			p += 4;
+		}
+		printf("\n");
+	}
+
+	/* Clean up. */
 	fz_drop_pixmap(ctx, pix);
-	fz_drop_page(ctx, page);
 	fz_drop_document(ctx, doc);
 	fz_drop_context(ctx);
-}
-
-int main(int argc, char **argv)
-{
-	char *filename = argc >= 2 ? argv[1] : "";
-	int pagenumber = argc > 2 ? atoi(argv[2]) : 1;
-	int zoom = argc > 3 ? atoi(argv[3]) : 100;
-	int rotation = argc > 4 ? atoi(argv[4]) : 0;
-
-	render(filename, pagenumber, zoom, rotation);
-
-	return 0;
+	return EXIT_SUCCESS;
 }