Attachment 50482 Details for Bug 4536 – align 1 pixel wide lines

[patch] align 1 pixel wide lines

0002-cairo-align-strokes-when-Stroke-Adjust-is-true-and-l.patch (text/plain), 4.95 KB, created by Adrian Johnson on 2011-08-23 04:57:15 UTC

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Creator: Adrian Johnson

Created: 2011-08-23 04:57:15 UTC

Size: 4.95 KB

patch

obsolete

>From 6e93cc6532b03fd59b2cf91013cc191eedd6344c Mon Sep 17 00:00:00 2001
>From: Adrian Johnson <ajohnson@redneon.com>
>Date: Tue, 23 Aug 2011 21:02:02 +0930
>Subject: [PATCH 2/2] cairo: align strokes when Stroke Adjust is true and line width <= 1
>
>If the stroke coordinates are not aligned, lines in cairo may be up to
>1 pixel wider than the requested width. This is most obvious when the
>line width is 1 and the rendered line is 2 pixels.
>
>When Stroke Adjust is true, the PDF standard requires that stroke
>coordinates be adjusted to ensure the stroke width is within half a
>pixel of the requested width.
>
>If Stroke Adjust is enabled and the width is <= 1 pixel (the previous
>commit adjusts the width to be at least 1 pixel), use the method
>documented at http://www.cairographics.org/FAQ/#sharp_lines to align
>the coordinates to ensure the rendered width is 1 pixel.
>---
> poppler/CairoOutputDev.cc |   40 +++++++++++++++++++++++++++++++++++-----
> poppler/CairoOutputDev.h  |    3 +++
> 2 files changed, 38 insertions(+), 5 deletions(-)
>
>diff --git a/poppler/CairoOutputDev.cc b/poppler/CairoOutputDev.cc
>index 272ae55..1071cba 100644
>--- a/poppler/CairoOutputDev.cc
>+++ b/poppler/CairoOutputDev.cc
>@@ -157,6 +157,8 @@ CairoOutputDev::CairoOutputDev() {
>   // the SA parameter supposedly defaults to false, but Acrobat
>   // apparently hardwires it to true
>   stroke_adjust = globalParams->getStrokeAdjust();
>+  align_stroke_coords = gFalse;
>+  adjusted_stroke_width = gFalse;
> }
> 
> CairoOutputDev::~CairoOutputDev() {
>@@ -412,6 +414,7 @@ void CairoOutputDev::updateMiterLimit(GfxState *state) {
> 
> void CairoOutputDev::updateLineWidth(GfxState *state) {
>   LOG(printf ("line width: %f\n", state->getLineWidth()));
>+  adjusted_stroke_width = gFalse;
>   if (state->getLineWidth() == 0.0) {
>     /* find out how big pixels (device unit) are in the x and y directions
>      * choose the smaller of the two as our line width */
>@@ -431,11 +434,12 @@ void CairoOutputDev::updateLineWidth(GfxState *state) {
> 
>       /* find out line width in device units */
>       cairo_user_to_device_distance(cairo, &x, &y);
>-      if (x < 0.5 && y < 0.5) {
>+      if (x <= 1.0 && y <= 1.0) {
> 	/* adjust width to at least one device pixel */
>-	x = y = 0.5;
>+	x = y = 1.0;
> 	cairo_device_to_user_distance(cairo, &x, &y);
> 	width = MIN(fabs(x),fabs(y));
>+	adjusted_stroke_width = gTrue;
>       }
>     }
>     cairo_set_line_width (cairo, width);
>@@ -632,6 +636,15 @@ void CairoOutputDev::updateFont(GfxState *state) {
>   cairo_set_font_matrix (cairo, &matrix);
> }
> 
>+void CairoOutputDev::alignStrokeCoords(double *x, double *y)
>+{
>+  /* see http://www.cairographics.org/FAQ/#sharp_lines */
>+  cairo_user_to_device (cairo, x, y);
>+  *x = floor(*x) + 0.5;
>+  *y = floor(*y) + 0.5;
>+  cairo_device_to_user (cairo, x, y);
>+}
>+
> void CairoOutputDev::doPath(cairo_t *cairo, GfxState *state, GfxPath *path) {
>   GfxSubpath *subpath;
>   int i, j;
>@@ -639,8 +652,15 @@ void CairoOutputDev::doPath(cairo_t *cairo, GfxState *state, GfxPath *path) {
>   for (i = 0; i < path->getNumSubpaths(); ++i) {
>     subpath = path->getSubpath(i);
>     if (subpath->getNumPoints() > 0) {
>-      cairo_move_to (cairo, subpath->getX(0), subpath->getY(0));
>-         j = 1;
>+      if (align_stroke_coords) {
>+	double x = subpath->getX(0);
>+	double y = subpath->getY(0);
>+	alignStrokeCoords(&x, &y);
>+	cairo_move_to (cairo, x, y);
>+      } else {
>+	cairo_move_to (cairo, subpath->getX(0), subpath->getY(0));
>+      }
>+      j = 1;
>       while (j < subpath->getNumPoints()) {
> 	if (subpath->getCurve(j)) {
> 	  cairo_curve_to( cairo,
>@@ -650,7 +670,14 @@ void CairoOutputDev::doPath(cairo_t *cairo, GfxState *state, GfxPath *path) {
> 
> 	  j += 3;
> 	} else {
>-	  cairo_line_to (cairo, subpath->getX(j), subpath->getY(j));
>+	  if (align_stroke_coords) {
>+	    double x = subpath->getX(j);
>+	    double y = subpath->getY(j);
>+	    alignStrokeCoords(&x, &y);
>+	    cairo_line_to (cairo, x, y);
>+	  } else {
>+	    cairo_line_to (cairo, subpath->getX(j), subpath->getY(j));
>+	  }
> 	  ++j;
> 	}
>       }
>@@ -670,7 +697,10 @@ void CairoOutputDev::stroke(GfxState *state) {
> 	  return;
>   }
> 
>+  if (adjusted_stroke_width)
>+    align_stroke_coords = gTrue;
>   doPath (cairo, state, state->getPath());
>+  align_stroke_coords = gFalse;
>   cairo_set_source (cairo, stroke_pattern);
>   LOG(printf ("stroke\n"));
>   cairo_stroke (cairo);
>diff --git a/poppler/CairoOutputDev.h b/poppler/CairoOutputDev.h
>index 7cf4157..effa9dd 100644
>--- a/poppler/CairoOutputDev.h
>+++ b/poppler/CairoOutputDev.h
>@@ -282,12 +282,15 @@ protected:
>   GBool getStreamData (Stream *str, char **buffer, int *length);
>   void setMimeData(Stream *str, Object *ref, cairo_surface_t *image);
>   void fillToStrokePathClip();
>+  void alignStrokeCoords(double *x, double *y);
> 
>   GfxRGB fill_color, stroke_color;
>   cairo_pattern_t *fill_pattern, *stroke_pattern;
>   double fill_opacity;
>   double stroke_opacity;
>   GBool stroke_adjust;
>+  GBool adjusted_stroke_width;
>+  GBool align_stroke_coords;
>   CairoFont *currentFont;
> 
>   struct StrokePathClip {
>-- 
>1.7.4.1
>

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