path: root/pdf/pdf_page.c

#include "fitz.h"
#include "mupdf.h"

struct info
{
	fz_obj *resources;
	fz_obj *mediabox;
	fz_obj *cropbox;
	fz_obj *rotate;
};

int
pdf_count_pages(pdf_xref *xref)
{
	return xref->page_len;
}

int
pdf_find_page_number(pdf_xref *xref, fz_obj *page)
{
	int i, num = fz_to_num(page);
	for (i = 0; i < xref->page_len; i++)
		if (num == fz_to_num(xref->page_refs[i]))
			return i;
	return -1;
}

static void
put_marker_bool(fz_context *ctx, fz_obj *rdb, char *marker, int val)
{
	fz_obj *tmp;

	tmp = fz_new_bool(ctx, val);
	fz_try(ctx)
	{
		fz_dict_puts(rdb, marker, tmp);
	}
	fz_catch(ctx)
	{
		fz_drop_obj(tmp);
		fz_rethrow(ctx);
	}
	fz_drop_obj(tmp);
}

static void
pdf_load_page_tree_node(pdf_xref *xref, fz_obj *node, struct info info)
{
	fz_obj *dict, *kids, *count;
	fz_obj *obj;
	int i, n;
	fz_context *ctx = xref->ctx;

	/* prevent infinite recursion */
	if (!node || fz_dict_mark(node))
		return;

	fz_try(ctx)
	{
		kids = fz_dict_gets(node, "Kids");
		count = fz_dict_gets(node, "Count");

		if (fz_is_array(kids) && fz_is_int(count))
		{
			obj = fz_dict_gets(node, "Resources");
			if (obj)
				info.resources = obj;
			obj = fz_dict_gets(node, "MediaBox");
			if (obj)
				info.mediabox = obj;
			obj = fz_dict_gets(node, "CropBox");
			if (obj)
				info.cropbox = obj;
			obj = fz_dict_gets(node, "Rotate");
			if (obj)
				info.rotate = obj;

			n = fz_array_len(kids);
			for (i = 0; i < n; i++)
			{
				obj = fz_array_get(kids, i);
				pdf_load_page_tree_node(xref, obj, info);
			}
		}
		else
		{
			dict = fz_resolve_indirect(node);

			if (info.resources && !fz_dict_gets(dict, "Resources"))
				fz_dict_puts(dict, "Resources", info.resources);
			if (info.mediabox && !fz_dict_gets(dict, "MediaBox"))
				fz_dict_puts(dict, "MediaBox", info.mediabox);
			if (info.cropbox && !fz_dict_gets(dict, "CropBox"))
				fz_dict_puts(dict, "CropBox", info.cropbox);
			if (info.rotate && !fz_dict_gets(dict, "Rotate"))
				fz_dict_puts(dict, "Rotate", info.rotate);

			if (xref->page_len == xref->page_cap)
			{
				fz_warn(ctx, "found more pages than expected");
				xref->page_cap ++;
				xref->page_refs = fz_resize_array(ctx, xref->page_refs, xref->page_cap, sizeof(fz_obj*));
				xref->page_objs = fz_resize_array(ctx, xref->page_objs, xref->page_cap, sizeof(fz_obj*));
			}

			xref->page_refs[xref->page_len] = fz_keep_obj(node);
			xref->page_objs[xref->page_len] = fz_keep_obj(dict);
			xref->page_len ++;
		}
	}
	fz_catch(ctx)
	{
		fz_dict_unmark(node);
		fz_rethrow(ctx);
	}
	fz_dict_unmark(node);
}

void
pdf_load_page_tree(pdf_xref *xref)
{
	struct info info;
	fz_context *ctx = xref->ctx;
	fz_obj *catalog = fz_dict_gets(xref->trailer, "Root");
	fz_obj *pages = fz_dict_gets(catalog, "Pages");
	fz_obj *count = fz_dict_gets(pages, "Count");

	if (!fz_is_dict(pages))
		fz_throw(ctx, "missing page tree");
	if (!fz_is_int(count))
		fz_throw(ctx, "missing page count");

	xref->page_cap = fz_to_int(count);
	xref->page_len = 0;
	xref->page_refs = fz_malloc_array(ctx, xref->page_cap, sizeof(fz_obj*));
	xref->page_objs = fz_malloc_array(ctx, xref->page_cap, sizeof(fz_obj*));

	info.resources = NULL;
	info.mediabox = NULL;
	info.cropbox = NULL;
	info.rotate = NULL;

	pdf_load_page_tree_node(xref, pages, info);
}

/* We need to know whether to install a page-level transparency group */

static int pdf_resources_use_blending(fz_context *ctx, fz_obj *rdb);

static int
pdf_extgstate_uses_blending(fz_context *ctx, fz_obj *dict)
{
	fz_obj *obj = fz_dict_gets(dict, "BM");
	if (fz_is_name(obj) && strcmp(fz_to_name(obj), "Normal"))
		return 1;
	return 0;
}

static int
pdf_pattern_uses_blending(fz_context *ctx, fz_obj *dict)
{
	fz_obj *obj;
	obj = fz_dict_gets(dict, "Resources");
	if (pdf_resources_use_blending(ctx, obj))
		return 1;
	obj = fz_dict_gets(dict, "ExtGState");
	return pdf_extgstate_uses_blending(ctx, obj);
}

static int
pdf_xobject_uses_blending(fz_context *ctx, fz_obj *dict)
{
	fz_obj *obj = fz_dict_gets(dict, "Resources");
	return pdf_resources_use_blending(ctx, obj);
}

static int
pdf_resources_use_blending(fz_context *ctx, fz_obj *rdb)
{
	fz_obj *obj;
	int i, n, useBM = 0;

	if (!rdb)
		return 0;

	/* Have we been here before and stashed an answer? */
	obj = fz_dict_gets(rdb, ".useBM");
	if (obj)
		return fz_to_bool(obj);

	/* stop on cyclic resource dependencies */
	if (fz_dict_mark(rdb))
		return 0;

	fz_try(ctx)
	{
		obj = fz_dict_gets(rdb, "ExtGState");
		n = fz_dict_len(obj);
		for (i = 0; i < n; i++)
			if (pdf_extgstate_uses_blending(ctx, fz_dict_get_val(obj, i)))
				goto found;

		obj = fz_dict_gets(rdb, "Pattern");
		n = fz_dict_len(obj);
		for (i = 0; i < n; i++)
			if (pdf_pattern_uses_blending(ctx, fz_dict_get_val(obj, i)))
				goto found;

		obj = fz_dict_gets(rdb, "XObject");
		n = fz_dict_len(obj);
		for (i = 0; i < n; i++)
			if (pdf_xobject_uses_blending(ctx, fz_dict_get_val(obj, i)))
				goto found;
		if (0)
		{
found:
			useBM = 1;
		}
	}
	fz_catch(ctx)
	{
		fz_dict_unmark(rdb);
		fz_rethrow(ctx);
	}
	fz_dict_unmark(rdb);

	put_marker_bool(ctx, rdb, ".useBM", useBM);
	return useBM;
}

/* we need to combine all sub-streams into one for the content stream interpreter */

static fz_buffer *
pdf_load_page_contents_array(pdf_xref *xref, fz_obj *list)
{
	fz_buffer *big;
	fz_buffer *one;
	int i, n;
	fz_context *ctx = xref->ctx;

	big = fz_new_buffer(ctx, 32 * 1024);

	n = fz_array_len(list);
	for (i = 0; i < n; i++)
	{
		fz_obj *stm = fz_array_get(list, i);
		fz_try(ctx)
		{
			one = pdf_load_stream(xref, fz_to_num(stm), fz_to_gen(stm));
		}
		fz_catch(ctx)
		{
			fz_warn(ctx, "cannot load content stream part %d/%d", i + 1, n);
			continue;
		}

		if (big->len + one->len + 1 > big->cap)
			fz_resize_buffer(ctx, big, big->len + one->len + 1);
		memcpy(big->data + big->len, one->data, one->len);
		big->data[big->len + one->len] = ' ';
		big->len += one->len + 1;

		fz_drop_buffer(ctx, one);
	}

	if (n > 0 && big->len == 0)
	{
		fz_drop_buffer(ctx, big);
		fz_throw(ctx, "cannot load content stream");
	}

	return big;
}

static fz_buffer *
pdf_load_page_contents(pdf_xref *xref, fz_obj *obj)
{
	fz_context *ctx = xref->ctx;

	if (fz_is_array(obj))
	{
		return pdf_load_page_contents_array(xref, obj);
		/* RJW: "cannot load content stream array" */
	}
	else if (pdf_is_stream(xref, fz_to_num(obj), fz_to_gen(obj)))
	{
		return pdf_load_stream(xref, fz_to_num(obj), fz_to_gen(obj));
		/* RJW: "cannot load content stream (%d 0 R)", fz_to_num(obj) */
	}

	fz_warn(ctx, "page contents missing, leaving page blank");
	return fz_new_buffer(ctx, 0);
}

pdf_page *
pdf_load_page(pdf_xref *xref, int number)
{
	pdf_page *page;
	pdf_annot *annot;
	fz_obj *pageobj, *pageref;
	fz_obj *obj;
	fz_rect mediabox, cropbox;
	fz_context *ctx = xref->ctx;

	if (number < 0 || number >= xref->page_len)
		fz_throw(ctx, "cannot find page %d", number + 1);

	pageobj = xref->page_objs[number];
	pageref = xref->page_refs[number];

	page = fz_malloc_struct(ctx, pdf_page);
	page->resources = NULL;
	page->contents = NULL;
	page->transparency = 0;
	page->links = NULL;
	page->annots = NULL;

	mediabox = pdf_to_rect(ctx, fz_dict_gets(pageobj, "MediaBox"));
	if (fz_is_empty_rect(mediabox))
	{
		fz_warn(ctx, "cannot find page size for page %d", number + 1);
		mediabox.x0 = 0;
		mediabox.y0 = 0;
		mediabox.x1 = 612;
		mediabox.y1 = 792;
	}

	cropbox = pdf_to_rect(ctx, fz_dict_gets(pageobj, "CropBox"));
	if (!fz_is_empty_rect(cropbox))
		mediabox = fz_intersect_rect(mediabox, cropbox);

	page->mediabox.x0 = MIN(mediabox.x0, mediabox.x1);
	page->mediabox.y0 = MIN(mediabox.y0, mediabox.y1);
	page->mediabox.x1 = MAX(mediabox.x0, mediabox.x1);
	page->mediabox.y1 = MAX(mediabox.y0, mediabox.y1);

	if (page->mediabox.x1 - page->mediabox.x0 < 1 || page->mediabox.y1 - page->mediabox.y0 < 1)
	{
		fz_warn(ctx, "invalid page size in page %d", number + 1);
		page->mediabox = fz_unit_rect;
	}

	page->rotate = fz_to_int(fz_dict_gets(pageobj, "Rotate"));

	obj = fz_dict_gets(pageobj, "Annots");
	if (obj)
	{
		pdf_load_links(&page->links, xref, obj);
		pdf_load_annots(&page->annots, xref, obj);
	}

	page->resources = fz_dict_gets(pageobj, "Resources");
	if (page->resources)
		fz_keep_obj(page->resources);

	obj = fz_dict_gets(pageobj, "Contents");
	fz_try(ctx)
	{
		page->contents = pdf_load_page_contents(xref, obj);

		if (pdf_resources_use_blending(ctx, page->resources))
			page->transparency = 1;

		for (annot = page->annots; annot && !page->transparency; annot = annot->next)
			if (pdf_resources_use_blending(ctx, annot->ap->resources))
				page->transparency = 1;
	}
	fz_catch(ctx)
	{
		pdf_free_page(ctx, page);
		fz_throw(ctx, "cannot load page %d contents (%d 0 R)", number + 1, fz_to_num(pageref));
	}

	return page;
}

void
pdf_free_page(fz_context *ctx, pdf_page *page)
{
	if (page->resources)
		fz_drop_obj(page->resources);
	if (page->contents)
		fz_drop_buffer(ctx, page->contents);
	if (page->links)
		fz_free_link(ctx, page->links);
	if (page->annots)
		pdf_free_annot(ctx, page->annots);
	fz_free(ctx, page);
}