Implement covered text handling.

CMakeLists.txt

@@ -161,6 +161,8 @@ set(PDF2HTMLEX_SRC ${PDF2HTMLEX_SRC}
     src/Base64Stream.cc
     src/Color.h
     src/Color.cc
+    src/CoveredTextHandler.h
+    src/CoveredTextHandler.cc
     src/HTMLState.h
     src/HTMLTextLine.h
     src/HTMLTextLine.cc

pdf2htmlEX.1.in

@@ -242,6 +242,11 @@ If set to 0, pdf2htmlEX would try its best to balance the two methods above.
 .B --optimize-text <0|1> (Default: 0)
 If set to 1, pdf2htmlEX will try to reduce the number of HTML elements used for text. Turn it off if anything goes wrong.
 
+.TP
+.B --process-covered-text <0|1> (Default: 0)
+If set to 1, pdf2htmlEX will try to detect texts covered by other graphics and properly arrange them, 
+i.e. covered texts are made transparent in text layer, and are drawn on background layer.
+
 .SS Background Image
 
 .TP

src/BackgroundRenderer/CairoBackgroundRenderer.cc

@@ -63,6 +63,13 @@ void CairoBackgroundRenderer::drawChar(GfxState *state, double x, double y,
     {
         CairoOutputDev::drawChar(state,x,y,dx,dy,originX,originY,code,nBytes,u,uLen);
     }
+    // If a char is treated as image, it is not subject to cover test
+    // (see HTMLRenderer::drawString), so don't increase drawn_char_count.
+    else if (param.process_covered_text) {
+        if (html_renderer->get_chars_covered()[drawn_char_count])
+            CairoOutputDev::drawChar(state,x,y,dx,dy,originX,originY,code,nBytes,u,uLen);
+        drawn_char_count++;
+    }
 }
 
 void CairoBackgroundRenderer::beginTextObject(GfxState *state)
@@ -97,6 +104,7 @@ static GBool annot_cb(Annot *, void * pflag) {
 
 bool CairoBackgroundRenderer::render_page(PDFDoc * doc, int pageno)
 {
+    drawn_char_count = 0;
     double page_width;
     double page_height;
     if(param.use_cropbox)

src/BackgroundRenderer/CairoBackgroundRenderer.h

@@ -66,6 +66,7 @@ private:
   std::unordered_map<int, int> bitmaps_ref_count;
   // id of bitmaps' stream used by current page
   std::vector<int> bitmaps_in_current_page;
+  int drawn_char_count;
 };
 
 }

src/CoveredTextHandler.cc

@@ -0,0 +1,55 @@
+/*
+ * CoveredTextHandler.cc
+ *
+ *  Created on: 2014-6-14
+ *      Author: duanyao
+ */
+
+#include "CoveredTextHandler.h"
+
+#include "util/math.h"
+
+namespace pdf2htmlEX {
+
+CoveredTextHandler::CoveredTextHandler()
+{
+    // TODO Auto-generated constructor stub
+
+}
+
+CoveredTextHandler::~CoveredTextHandler()
+{
+    // TODO Auto-generated destructor stub
+}
+
+void CoveredTextHandler::reset()
+{
+    char_bboxes.clear();
+    chars_covered.clear();
+}
+
+void CoveredTextHandler::add_char_bbox(double * bbox)
+{
+    for (int i = 0; i < 4; i++)
+        char_bboxes.push_back(bbox[i]);
+    chars_covered.push_back(false);
+}
+
+void CoveredTextHandler::add_non_char_bbox(double * bbox, int index)
+{
+    if (index < 0)
+        index = chars_covered.size();
+    for (int i = 0; i < index; i++)
+    {
+        if (chars_covered[i])
+            continue;
+        double * cbbox = &char_bboxes[i * 4];
+        if (bbox_intersect(cbbox, bbox))
+        {
+            chars_covered[i] = true;
+            add_non_char_bbox(cbbox, i);
+        }
+    }
+}
+
+}

src/CoveredTextHandler.h

@@ -0,0 +1,62 @@
+/*
+ * CoveredTextHandler.h
+ *
+ *  Created on: 2014-6-14
+ *      Author: duanyao
+ */
+
+#ifndef COVEREDTEXTHANDLER_H__
+#define COVEREDTEXTHANDLER_H__
+
+#include <vector>
+
+namespace pdf2htmlEX {
+
+/**
+ * Detect characters that are covered by non-char graphics on a page.
+ */
+class CoveredTextHandler
+{
+public:
+    CoveredTextHandler();
+    virtual ~CoveredTextHandler();
+
+    /**
+     * Reset to initial state. Should be called when start drawing a page.
+     */
+    void reset();
+
+    /**
+     * Add a drawn character's bounding box.
+     * @param bbox (x0, y0, x1, y1)
+     */
+    void add_char_bbox(double * bbox);
+
+    /**
+     * Add a drawn non-char graphics' bounding box.
+     * If it intersects any previously drawn char's bbox, the char is marked as covered
+     * and treated as an non-char.
+     * @param bbox (x0, y0, x1, y1)
+     * @param index this graphics' drawing order: assume it is drawn after (index-1)th
+     *   char. -1 means after the last char.
+     */
+    void add_non_char_bbox(double * bbox, int index = -1);
+
+    /**
+     * An array of flags indicating whether a char is covered by any non-char graphics.
+     * Index by the order that these chars are added.
+     * This vector grows as add_char_bbox() is called, so its size is the count
+     * of currently drawn chars.
+     */
+    const std::vector<bool> & get_chars_covered() { return chars_covered; }
+
+private:
+    //covered text test
+    std::vector<bool> chars_covered;
+    // x00, y00, x01, y01; x10, y10, x11, y11;...
+    std::vector<double> char_bboxes;
+};
+
+}
+
+#endif /* COVEREDTEXTHANDLER_H__ */

src/HTMLRenderer/HTMLRenderer.h

@@ -31,6 +31,7 @@
 #include "HTMLTextPage.h"
 
 #include "BackgroundRenderer/BackgroundRenderer.h"
+#include "CoveredTextHandler.h"
 
 #include "util/const.h"
 #include "util/misc.h"
@@ -125,6 +126,15 @@ public:
 
     virtual void drawImage(GfxState * state, Object * ref, Stream * str, int width, int height, GfxImageColorMap * colorMap, GBool interpolate, int *maskColors, GBool inlineImg);
 
+    virtual void drawSoftMaskedImage(GfxState *state, Object *ref, Stream *str,
+                       int width, int height,
+                       GfxImageColorMap *colorMap,
+                       GBool interpolate,
+                       Stream *maskStr,
+                       int maskWidth, int maskHeight,
+                       GfxImageColorMap *maskColorMap,
+                       GBool maskInterpolate);
+
     virtual void stroke(GfxState *state) { css_do_path(state, false); }
     virtual void fill(GfxState *state) { css_do_path(state, true); }
     virtual GBool axialShadedFill(GfxState *state, GfxAxialShading *shading, double tMin, double tMax);
@@ -135,6 +145,8 @@ public:
     bool can_stroke(GfxState *state) { return css_do_path(state, false, true); }
     bool can_fill(GfxState *state) { return css_do_path(state, true, true); }
 
+    const std::vector<bool> & get_chars_covered() { return covered_text_handler.get_chars_covered(); }
+
 protected:
     ////////////////////////////////////////////////////
     // misc
@@ -215,6 +227,19 @@ protected:
             const GfxRGB * line_color, const GfxRGB * fill_color, 
             void (*style_function)(void *, std::ostream &) = nullptr, void * style_function_data = nullptr );
 
+    ////////////////////////////////////////////////////
+    // Covered text handling
+    ////////////////////////////////////////////////////
+    /*
+     * Cue CoveredTextHandler that a character is drawn
+     * x, y: glyph-drawing position, in PDF text object space.
+     * ax, ay: glyph advance, in glyph space.
+     */
+    void add_char_bbox(GfxState *state, double x, double y, double ax, double ay);
+    /*
+     * Cue CoveredTextHandler that an image is drawn
+     */
+    void add_image_bbox(GfxState *state);
 
     ////////////////////////////////////////////////////
     // PDF stuffs
@@ -338,6 +363,8 @@ protected:
     std::string cur_page_filename;
 
     static const std::string MANIFEST_FILENAME;
+
+    CoveredTextHandler covered_text_handler;
 };
 
 } //namespace pdf2htmlEX

src/HTMLRenderer/general.cc

@@ -133,13 +133,10 @@ void HTMLRenderer::process(PDFDoc *doc)
             cur_page_filename = filled_template_filename;
         }
 
-        if(param.process_nontext)
-        {
-            fallback_bg_required = !bg_renderer->render_page(doc, i);
-            if (fallback_bg_required && fallback_bg_renderer != nullptr)
-                fallback_bg_renderer->render_page(doc, i);
-        }
-
+        // We handle covered texts during doc->displayPage(this...),
+        // and bg_renderer->render_page() depends on the result, so it must be called after
+        // doc->displayPage(this...).
+        covered_text_handler.reset();
         doc->displayPage(this, i,
                 text_zoom_factor() * DEFAULT_DPI, text_zoom_factor() * DEFAULT_DPI,
                 0,
@@ -148,6 +145,13 @@ void HTMLRenderer::process(PDFDoc *doc)
                 false, // printing
                 nullptr, nullptr, nullptr, nullptr);
 
+        if(param.process_nontext)
+        {
+            fallback_bg_required = !bg_renderer->render_page(doc, i);
+            if (fallback_bg_required && fallback_bg_renderer != nullptr)
+                fallback_bg_renderer->render_page(doc, i);
+        }
+
         if(param.split_pages)
         {
             delete f_curpage;

src/HTMLRenderer/image.cc

@@ -14,6 +14,8 @@ namespace pdf2htmlEX {
 
 void HTMLRenderer::drawImage(GfxState * state, Object * ref, Stream * str, int width, int height, GfxImageColorMap * colorMap, GBool interpolate, int *maskColors, GBool inlineImg)
 {
+    add_image_bbox(state);
+
     return OutputDev::drawImage(state,ref,str,width,height,colorMap,interpolate,maskColors,inlineImg);
 
 #if 0
@@ -62,4 +64,30 @@ void HTMLRenderer::drawImage(GfxState * state, Object * ref, Stream * str, int w
 #endif
 }
 
+void HTMLRenderer::drawSoftMaskedImage(GfxState *state, Object *ref, Stream *str,
+                   int width, int height,
+                   GfxImageColorMap *colorMap,
+                   GBool interpolate,
+                   Stream *maskStr,
+                   int maskWidth, int maskHeight,
+                   GfxImageColorMap *maskColorMap,
+                   GBool maskInterpolate)
+{
+    add_image_bbox(state);
+
+    return OutputDev::drawSoftMaskedImage(state,ref,str,
+            width,height,colorMap,interpolate,
+            maskStr, maskWidth, maskHeight, maskColorMap, maskInterpolate);
+}
+
+void HTMLRenderer::add_image_bbox(GfxState *state)
+{
+    if (!param.process_covered_text)
+        return;
+    auto ctm = state->getCTM();
+    double bbox[4] {0, 0, 1, 1};
+    tm_transform_bbox(ctm, bbox);
+    covered_text_handler.add_non_char_bbox(bbox);
+}
+
 } // namespace pdf2htmlEX

src/HTMLRenderer/state.cc

@@ -119,6 +119,9 @@ void HTMLRenderer::reset_state()
     cur_line_state.y = 0;
     memcpy(cur_line_state.transform_matrix, ID_MATRIX, sizeof(cur_line_state.transform_matrix));
 
+    if (param.process_covered_text)
+        cur_line_state.chars_covered = &covered_text_handler.get_chars_covered();
+
     cur_clip_state.xmin = 0;
     cur_clip_state.xmax = 0;
     cur_clip_state.ymin = 0;
@@ -502,6 +505,8 @@ void HTMLRenderer::prepare_text_line(GfxState * state)
         double rise_x, rise_y;
         state->textTransformDelta(0, state->getRise(), &rise_x, &rise_y);
         state->transform(state->getCurX() + rise_x, state->getCurY() + rise_y, &cur_line_state.x, &cur_line_state.y);
+        if (param.process_covered_text)
+            cur_line_state.first_char_index = covered_text_handler.get_chars_covered().size();
         html_text_page.open_new_line(cur_line_state);
 
         cur_text_state.vertical_align = 0;

src/HTMLRenderer/text.cc

@@ -72,6 +72,8 @@ void HTMLRenderer::drawString(GfxState * state, GooString * s)
             cerr << "TODO: non-zero origins" << endl;
         }
 
+        add_char_bbox(state, dx, dy, dx1, dy1);
+
         bool is_space = false;
         if (n == 1 && *p == ' ') 
         {
@@ -143,4 +145,43 @@ void HTMLRenderer::drawString(GfxState * state, GooString * s)
     draw_ty += dy;
 }
 
+void HTMLRenderer::add_char_bbox(GfxState *state, double x, double y, double ax, double ay)
+{
+    if (!param.process_covered_text)
+        return;
+
+    Matrix tm_ctm, tm, itm;
+    memcpy(tm_ctm.m, this->cur_text_tm, sizeof(tm_ctm.m));
+    memcpy(tm.m, state->getTextMat(), sizeof(tm.m));
+    double fs = state->getFontSize();
+
+    double cx = state->getCurX(), cy = state->getCurY(),
+            ry = state->getRise(), h = state->getHorizScaling();
+
+    //cx and cy has been transformed by text matrix, we need to reverse them.
+    tm.invertTo(&itm);
+    double char_cx, char_cy;
+    itm.transform(cx, cy, &char_cx, &char_cy);
+
+    //TODO Vertical? Currently vertical/type3 chars are treated as non-chars.
+    double tchar[6] {fs * h, 0, 0, fs, char_cx + x, char_cy + y + ry};
+
+    double tfinal[6];
+    tm_multiply(tfinal, tm_ctm.m, tchar);
+
+    auto font = state->getFont();
+    double bbox[4] {0, 0, ax, ay};
+    double desc = font->getDescent(), asc = font->getAscent();
+    if (font->getWMode() == 0)
+    {
+        bbox[1] += desc;
+        bbox[3] += asc;
+    }
+    else
+    {//TODO Vertical?
+    }
+    tm_transform_bbox(tfinal, bbox);
+    covered_text_handler.add_char_bbox(bbox);
+}
+
 } // namespace pdf2htmlEX

src/HTMLState.h

@@ -62,6 +62,9 @@ struct HTMLLineState
 {
     double x,y;
     double transform_matrix[4];
+    // The page-cope char index(in drawing order) of the first char in this line.
+    int first_char_index = -1;
+    const std::vector<bool> * chars_covered = nullptr;
 };
 
 struct HTMLClipState

src/HTMLTextLine.cc

@@ -69,6 +69,32 @@ void HTMLTextLine::append_state(const HTMLTextState & text_state)
     last_state.font_size *= last_state.font_info->font_size_scale;
 }
 
+void HTMLTextLine::dump_chars(ostream & out, const Unicode * u, int uLen)
+{
+    if (!line_state.chars_covered)
+    {
+        writeUnicodes(out, u, uLen);
+        return;
+    }
+
+    //TODO merge sibling invisiable spans
+    int start = this->line_state.first_char_index + dumped_char_count;
+    for(int i = 0; i < uLen; i++)
+    {
+        if (!(*line_state.chars_covered)[start + i]) //visible
+        {
+            writeUnicodes(out, u + i, 1);
+        }
+        else
+        {
+            out << "<span style=\"color:transparent\">";
+            writeUnicodes(out, u + i, 1);
+            out << "</span>";
+        }
+    }
+    dumped_char_count += uLen;
+}
+
 void HTMLTextLine::dump_text(ostream & out)
 {
     /*
@@ -84,6 +110,8 @@ void HTMLTextLine::dump_text(ostream & out)
         return;
     }
 
+    dumped_char_count = 0;
+
     // Start Output
     {
         // open <div> for the current text line
@@ -216,7 +244,7 @@ void HTMLTextLine::dump_text(ostream & out)
                 size_t next_text_idx = text_idx2;
                 if((cur_offset_iter != offsets.end()) && (cur_offset_iter->start_idx) < next_text_idx)
                     next_text_idx = cur_offset_iter->start_idx;
-                writeUnicodes(out, (&text.front()) + cur_text_idx, next_text_idx - cur_text_idx);
+                dump_chars(out, (&text.front()) + cur_text_idx, next_text_idx - cur_text_idx);
                 cur_text_idx = next_text_idx;
             }
         }

src/HTMLTextLine.h

@@ -91,6 +91,7 @@ public:
 private:
     void optimize_normal(std::vector<HTMLTextLine*> &);
     void optimize_aggressive(std::vector<HTMLTextLine*> &);
+    void dump_chars(std::ostream & out, const Unicode * u, int uLen);
 
     const Param & param;
     AllStateManager & all_manager;
@@ -103,6 +104,8 @@ private:
     std::vector<State> states;
     std::vector<Offset> offsets;
     std::vector<Unicode> text;
+
+    int dumped_char_count;
 };
 
 } // namespace pdf2htmlEX

src/Param.h

@@ -38,6 +38,7 @@ struct Param
     int process_nontext;
     int process_outline;
     int process_annotation;
+    int process_covered_text;
     int printing;
     int fallback;
     int tmp_file_size_limit;

src/pdf2htmlEX.cc

@@ -187,6 +187,7 @@ void parse_options (int argc, char **argv)
         .add("space-as-offset", &param.space_as_offset, 0, "treat space characters as offsets")
         .add("tounicode", &param.tounicode, 0, "how to handle ToUnicode CMaps (0=auto, 1=force, -1=ignore)")
         .add("optimize-text", &param.optimize_text, 0, "try to reduce the number of HTML elements used for text")
+        .add("process-covered-text", &param.process_covered_text, 0, "try to detect texts covered by other graphics and properly arrange them")
 
         // background image
         .add("bg-format", &param.bg_format, "png", "specify background image format")

src/util/math.bk.cc

@@ -0,0 +1,72 @@
+#include <cstring>
+#include <limits>
+#include <algorithm>
+
+#include "math.h"
+
+using std::min;
+using std::max;
+
+namespace pdf2htmlEX {
+
+void tm_transform(const double * tm, double & x, double & y, bool is_delta)
+{
+    double xx = x, yy = y;
+    x = tm[0] * xx + tm[2] * yy;
+    y = tm[1] * xx + tm[3] * yy;
+    if(!is_delta)
+    {
+        x += tm[4];
+        y += tm[5];
+    }
+}
+
+void tm_multiply(const double * tm_left, const double * tm_right, double * tm_result)
+{
+    double old[4];
+    memcpy(old, tm_left, sizeof(old));
+
+    tm_result[0] = tm_left[0] * tm_right[0] + tm_left[2] * tm_right[1];
+    tm_result[1] = tm_left[1] * tm_right[0] + tm_left[3] * tm_right[1];
+    tm_result[2] = tm_left[0] * tm_right[2] + tm_left[2] * tm_right[3];
+    tm_result[3] = tm_left[1] * tm_right[2] + tm_left[3] * tm_right[3];
+    tm_result[4] += tm_left[0] * tm_right[4] + tm_left[2] * tm_right[5];
+    tm_result[5] += tm_left[1] * tm_right[4] + tm_left[3] * tm_right[5];
+}
+
+void tm_transform_bbox(const double * tm, double * bbox)
+{
+    double & x1 = bbox[0];
+    double & y1 = bbox[1];
+    double & x2 = bbox[2];
+    double & y2 = bbox[3];
+    double _[4][2];
+    _[0][0] = _[1][0] = x1;
+    _[0][1] = _[2][1] = y1;
+    _[2][0] = _[3][0] = x2;
+    _[1][1] = _[3][1] = y2;
+
+    x1 = y1 = std::numeric_limits<double>::max();
+    x2 = y2 = std::numeric_limits<double>::min();
+    for(int i = 0; i < 4; ++i)
+    {
+        auto & x = _[i][0];
+        auto & y = _[i][1];
+        tm_transform(tm, x, y);
+        if(x < x1) x1 = x;
+        if(x > x2) x2 = x;
+        if(y < y1) y1 = y;
+        if(y > y2) y2 = y;
+    }
+}
+
+bool bbox_intersect(double * bbox1, double * bbox2)
+{
+    return min(bbox1[0], bbox1[2]) < max(bbox2[0], bbox2[2])
+        && max(bbox1[0], bbox1[2]) > min(bbox2[0], bbox2[2])
+        && min(bbox1[1], bbox1[3]) < max(bbox2[1], bbox2[3])
+        && max(bbox1[1], bbox1[3]) > min(bbox2[1], bbox2[3]);
+}
+
+} //namespace pdf2htmlEX 
+

src/util/math.cc

@@ -1,8 +1,12 @@
 #include <cstring>
 #include <limits>
+#include <algorithm>
 
 #include "math.h"
 
+using std::min;
+using std::max;
+
 namespace pdf2htmlEX {
 
 void tm_transform(const double * tm, double & x, double & y, bool is_delta)
@@ -56,5 +60,13 @@ void tm_transform_bbox(const double * tm, double * bbox)
     }
 }
 
+bool bbox_intersect(double * bbox1, double * bbox2)
+{
+    return min(bbox1[0], bbox1[2]) < max(bbox2[0], bbox2[2])
+        && max(bbox1[0], bbox1[2]) > min(bbox2[0], bbox2[2])
+        && min(bbox1[1], bbox1[3]) < max(bbox2[1], bbox2[3])
+        && max(bbox1[1], bbox1[3]) > min(bbox2[1], bbox2[3]);
+}
+
 } //namespace pdf2htmlEX 
 

src/util/math.h

@@ -40,5 +40,7 @@ void tm_transform(const double * tm, double & x, double & y, bool is_delta = fal
 void tm_multiply(double * tm_left, const double * tm_right);
 void tm_transform_bbox(const double * tm, double * bbox);
 
+bool bbox_intersect(double * bbox1, double * bbox2);
+
 } //namespace pdf2htmlEX 
 #endif //MATH_H__