Make the pdf device produce more efficient appearance streams for text

1 files changed, 60 insertions, 13 deletions

diff --git a/source/pdf/pdf-device.c b/source/pdf/pdf-device.c
index 0074f7eb..1ce80b17 100644
--- a/source/pdf/pdf-device.c
+++ b/source/pdf/pdf-device.c
@@ -1,5 +1,11 @@
 #include "mupdf/pdf.h"
 
+#include <ft2build.h>
+#include FT_FREETYPE_H
+#include FT_ADVANCES_H
+
+#define ALLOWED_TEXT_POS_ERROR (0.001f)
+
 typedef struct pdf_device_s pdf_device;
 
 typedef struct gstate_s gstate;
@@ -653,8 +659,9 @@ pdf_dev_pop(pdf_device *pdev)
 }
 
 static void
-pdf_dev_text(pdf_device *pdev, fz_text *text)
+pdf_dev_text(pdf_device *pdev, fz_text *text, float size)
 {
+	int mask = FT_LOAD_NO_SCALE | FT_LOAD_IGNORE_TRANSFORM;
 	int i;
 	fz_matrix trm;
 	fz_matrix inverse;
@@ -670,10 +677,14 @@ pdf_dev_text(pdf_device *pdev, fz_text *text)
 	trunc_trm.f = 0;
 	fz_invert_matrix(&inverse, &trunc_trm);
 
-	for (i=0; i < text->len; i++)
+	i = 0;
+	while (i < text->len)
 	{
 		fz_text_item *it = &text->items[i];
 		fz_point delta;
+		float x;
+		int j;
+
 		delta.x = it->x - trm.e;
 		delta.y = it->y - trm.f;
 		fz_transform_point(&delta, &inverse);
@@ -683,12 +694,32 @@ pdf_dev_text(pdf_device *pdev, fz_text *text)
 			trm.e = it->x;
 			trm.f = it->y;
 		}
-		/* FIXME: should use it->gid, rather than it->ucs, and convert
-		 * to the correct encoding */
-		fz_buffer_printf(pdev->ctx, gs->buf, "<%02x> Tj\n", it->ucs);
-		/* FIXME: Advance the text position - doesn't matter at the
-		 * moment as we absolutely position each glyph, but we should
-		 * use more efficient text outputting where possible. */
+
+		j = i+1;
+		if (text->font->ft_face)
+		{
+			/* Find prefix of text for which the advance of each character accounts
+			 * for the position offset */
+			x = it->x;
+			while (j < text->len)
+			{
+				FT_Fixed adv;
+				FT_Get_Advance(text->font->ft_face, text->items[j-1].gid, mask, &adv);
+				x += (float)adv * size /((FT_Face)text->font->ft_face)->units_per_EM;
+				if (fabs(x - text->items[j].x) > ALLOWED_TEXT_POS_ERROR || fabs(it->y - text->items[j].y) > ALLOWED_TEXT_POS_ERROR)
+					break;
+				j++;
+			}
+		}
+
+		fz_buffer_printf(pdev->ctx, gs->buf, "<");
+		for (i = i; i < j; i++)
+		{
+			/* FIXME: should use it->gid, rather than it->ucs, and convert
+			* to the correct encoding */
+			fz_buffer_printf(pdev->ctx, gs->buf, "%02x", text->items[i].ucs);
+		}
+		fz_buffer_printf(pdev->ctx, gs->buf, "> Tj\n");
 	}
 	gs->tm.e = trm.e;
 	gs->tm.f = trm.f;
@@ -913,7 +944,7 @@ pdf_dev_fill_text(fz_device *dev, fz_text *text, const fz_matrix *ctm,
 	pdf_dev_ctm(pdev, ctm);
 	pdf_dev_alpha(pdev, alpha, 0);
 	pdf_dev_color(pdev, colorspace, color, 0);
-	pdf_dev_text(pdev, text);
+	pdf_dev_text(pdev, text, size);
 }
 
 static void
@@ -921,46 +952,62 @@ pdf_dev_stroke_text(fz_device *dev, fz_text *text, fz_stroke_state *stroke, cons
 	fz_colorspace *colorspace, float *color, float alpha)
 {
 	pdf_device *pdev = dev->user;
+	fz_matrix trm = text->trm;
+	float size = fz_matrix_expansion(&trm);
+
+	fz_pre_scale(&trm, 1/size, 1/size);
 
 	pdf_dev_begin_text(pdev, &text->trm, 1);
 	pdf_dev_font(pdev, text->font, 1);
 	pdf_dev_ctm(pdev, ctm);
 	pdf_dev_alpha(pdev, alpha, 1);
 	pdf_dev_color(pdev, colorspace, color, 1);
-	pdf_dev_text(pdev, text);
+	pdf_dev_text(pdev, text, size);
 }
 
 static void
 pdf_dev_clip_text(fz_device *dev, fz_text *text, const fz_matrix *ctm, int accumulate)
 {
 	pdf_device *pdev = dev->user;
+	fz_matrix trm = text->trm;
+	float size = fz_matrix_expansion(&trm);
+
+	fz_pre_scale(&trm, 1/size, 1/size);
 
 	pdf_dev_begin_text(pdev, &text->trm, 0);
 	pdf_dev_ctm(pdev, ctm);
 	pdf_dev_font(pdev, text->font, 7);
-	pdf_dev_text(pdev, text);
+	pdf_dev_text(pdev, text, size);
 }
 
 static void
 pdf_dev_clip_stroke_text(fz_device *dev, fz_text *text, fz_stroke_state *stroke, const fz_matrix *ctm)
 {
 	pdf_device *pdev = dev->user;
+	fz_matrix trm = text->trm;
+	float size = fz_matrix_expansion(&trm);
+
+	fz_pre_scale(&trm, 1/size, 1/size);
 
 	pdf_dev_begin_text(pdev, &text->trm, 0);
 	pdf_dev_font(pdev, text->font, 5);
 	pdf_dev_ctm(pdev, ctm);
-	pdf_dev_text(pdev, text);
+	pdf_dev_text(pdev, text, size);
 }
 
 static void
 pdf_dev_ignore_text(fz_device *dev, fz_text *text, const fz_matrix *ctm)
 {
 	pdf_device *pdev = dev->user;
+	fz_matrix trm = text->trm;
+	float size = fz_matrix_expansion(&trm);
+
+	fz_pre_scale(&trm, 1/size, 1/size);
 
 	pdf_dev_begin_text(pdev, &text->trm, 0);
 	pdf_dev_ctm(pdev, ctm);
 	pdf_dev_font(pdev, text->font, 3);
-	pdf_dev_text(pdev, text);
+	pdf_dev_text(pdev, text, size);
 }
 
 static void