New Fl_ICO_Image class to read Windows .ico icon files

Many thanks to @darealshinji for contributing all the code
for this new FLTK image class (see branch Fl_ICO_Image of https://github.com/darealshinji/fltk).

CHANGES.txt

@@ -45,6 +45,7 @@ Changes in FLTK 1.4.0                            Released: ??? ?? 2022
     and Fl_Image::data_h() give the width and height of the image data.
   - New Fl_SVG_Image class: gives support of scalable vector graphics images
     to FLTK using the nanosvg software.
+  - New Fl_ICO_Image class to read Windows .ico icon files.
   - New classes Fl_SVG_File_Surface and Fl_EPS_File_Surface to save any FLTK
     graphics to SVG or EPS files, respectively.
   - Windows platform: added support for using a manifest to set the

FL/Fl_BMP_Image.H

@@ -1,7 +1,7 @@
 //
 // BMP image header file for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2021 by Bill Spitzak and others.
+// Copyright 1998-2022 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -34,7 +34,7 @@ public:
 
 protected:
 
-  void load_bmp_(class Fl_Image_Reader &rdr);
+  void load_bmp_(class Fl_Image_Reader &rdr, int ico_height = 0, int ico_width = 0);
 
 };
 

FL/Fl_ICO_Image.H

@@ -0,0 +1,55 @@
+//
+// ICO image header file for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2022 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     http://www.fltk.org/COPYING.php
+//
+// Please report all bugs and problems on the following page:
+//
+//     http://www.fltk.org/str.php
+//
+
+// https://en.wikipedia.org/wiki/ICO_(file_format)
+// http://www.daubnet.com/en/file-format-ico
+
+#ifndef Fl_ICO_Image_H
+#  define Fl_ICO_Image_H
+#  include "Fl_BMP_Image.H"
+
+/**
+ The Fl_ICO_Image class supports loading, caching, and drawing of Windows icon (.ico) files.
+ */
+class FL_EXPORT Fl_ICO_Image : public Fl_BMP_Image {
+
+public:
+  /** Windows ICONDIRENTRY structure  */
+   struct IconDirEntry {
+    int bWidth;         ///<  Image width
+    int bHeight;        ///<  Image height
+    int bColorCount;    ///<  Number of colors (0 if  ≥ 8bpp)
+    int bReserved;      ///<  Reserved
+    int wPlanes;        ///<  Color Planes
+    int wBitCount;      ///<  Bits per pixel
+    int dwBytesInRes;   ///<  Resource size in bytes
+    int dwImageOffset;  ///<  Offset to the image
+  };
+
+  Fl_ICO_Image(const char *filename, int id = -1, const unsigned char *data = NULL, const size_t datasize = 0);
+  ~Fl_ICO_Image();
+/** Gives the number of icons of various resolutions present in the ICO object */
+  int idcount() { return idcount_; }
+  /** Returns the array of idcount() loaded IconDirEntry structures */
+  IconDirEntry * const icondirentry() const { return icondirentry_; }
+
+private:
+  int idcount_;
+  struct IconDirEntry *icondirentry_;
+  void load_ico_(class Fl_Image_Reader &rdr, int id);
+};
+
+#endif // Fl_ICO_Image_H

FL/Fl_PNG_Image.H

@@ -1,7 +1,7 @@
 //
 // PNG image header file for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2021 by Bill Spitzak and others.
+// Copyright 1998-2022 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -28,13 +28,14 @@
   and alpha-based transparency.
 */
 class FL_EXPORT Fl_PNG_Image : public Fl_RGB_Image {
-
+  friend class Fl_ICO_Image;
 public:
 
   Fl_PNG_Image(const char* filename);
   Fl_PNG_Image (const char *name_png, const unsigned char *buffer, int datasize);
 private:
-  void load_png_(const char *name_png, const unsigned char *buffer_png, int datasize);
+  Fl_PNG_Image(const char *filename, int offset); // used by Fl_ICO_Image
+  void load_png_(const char *name_png, int offset, const unsigned char *buffer_png, int datasize);
 };
 
 // Support functions to write PNG image files (since 1.4.0)

src/CMakeLists.txt

@@ -465,6 +465,7 @@ set (IMGCPPFILES
   Fl_File_Icon2.cxx
   Fl_GIF_Image.cxx
   Fl_Help_Dialog.cxx
+  Fl_ICO_Image.cxx
   Fl_JPEG_Image.cxx
   Fl_PNG_Image.cxx
   Fl_PNM_Image.cxx

src/Fl_BMP_Image.cxx

@@ -1,7 +1,7 @@
 //
 // Fl_BMP_Image class for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 2011-2021 by Bill Spitzak and others.
+// Copyright 2011-2022 by Bill Spitzak and others.
 // Copyright 1997-2010 by Easy Software Products.
 // Image support by Matthias Melcher, Copyright 2000-2009.
 //
@@ -129,7 +129,7 @@ Fl_BMP_Image::Fl_BMP_Image(const char *imagename, const unsigned char *data, con
   format supports only 1 bit for alpha. To avoid code duplication, we use
   an Fl_Image_Reader that reads data from either a file or from memory.
 */
-void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr)
+void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr, int ico_height, int ico_width)
 {
   int   info_size,        // Size of info header
         width,            // Width of image (pixels)
@@ -147,7 +147,7 @@ void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr)
         row_order,        // 1 = normal;  -1 = flipped row order
         start_y,          // Beginning Y
         end_y;            // Ending Y
-  long  offbits;          // Offset to image data
+  long  offbits = 0;      // Offset to image data
   uchar bit,              // Bit in image
         byte;             // Byte in image
   uchar *ptr;             // Pointer into pixels
@@ -163,6 +163,7 @@ void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr)
   w(0); h(0); d(0); ld(0);      // make sure these are all zero
 
   // Get the header...
+  if (ico_height < 1) {
     byte = rdr.read_byte();       // Check "BM" sync chars
     bit  = rdr.read_byte();
     if (byte != 'B' || bit != 'M') {
@@ -174,6 +175,7 @@ void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr)
     rdr.read_word();              // Skip reserved stuff
     rdr.read_word();
     offbits = (long)rdr.read_dword();// Read offset to image data
+  }
 
   // Then the bitmap information...
   info_size = rdr.read_dword();
@@ -195,13 +197,21 @@ void Fl_BMP_Image::load_bmp_(Fl_Image_Reader &rdr)
     colors_used = 0;
 
     repcount = info_size - 12;
+  } else {
+    if (ico_height > 0 && ico_width > 0) {
+      rdr.read_long();
+      rdr.read_long();
+      width = ico_width;
+      height = ico_height;
     } else {
       // New BMP header...
-    width = rdr.read_long();
+      w(rdr.read_long());
       // If the height is negative, the row order is flipped
       temp = rdr.read_long();
       if (temp < 0) row_order = 1;
       height = abs(temp);
+    }
+
     rdr.read_word();
     depth = rdr.read_word();
     compression = rdr.read_dword();

src/Fl_ICO_Image.cxx

@@ -0,0 +1,202 @@
+//
+// Fl_ICO_Image class for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2022 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please report all bugs and problems on the following page:
+//
+//     https://www.fltk.org/str.php
+//
+
+
+//
+// Include necessary header files...
+//
+
+#include <FL/Fl.H>
+#include "config.h"
+#include "Fl_Image_Reader.h"
+#include <FL/Fl_ICO_Image.H>
+#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
+#  include <FL/Fl_PNG_Image.H>
+#endif
+
+/**
+ Loads the named icon image from the given .ico filename or from memory
+ \param filename Name of a .ico file, or of the in-memory image
+ \param id When id is -1 (default), the highest-resolution icon is loaded;
+ when id ≥ 0, load the icon with this ID;
+ when id = -2, load all IconDirEntry structures but no image.
+ \param data NULL, or in-memory icon data
+ \param datasize  Size  in bytes of the \p data byte array (used when \p data is not NULL)
+*/
+Fl_ICO_Image::Fl_ICO_Image(const char *filename, int id, const unsigned char *data, const size_t datasize)
+: Fl_BMP_Image(0,0),
+ idcount_(0),
+ icondirentry_(0)
+{
+  Fl_Image_Reader rdr;
+  int r;
+
+  w(0); h(0); d(0); ld(0);
+  alloc_array = 0;
+  array = 0;
+
+  if (data) {
+    r = rdr.open(filename, data, datasize);
+  } else {
+    r = rdr.open(filename);
+  }
+
+  if (r == -1) {
+    ld(ERR_FILE_ACCESS);
+  } else {
+    load_ico_(rdr, id);
+  }
+}
+
+/** Destructor */
+Fl_ICO_Image::~Fl_ICO_Image() {
+  delete[] icondirentry_;
+}
+
+
+/*
+ This method attempts to load the biggest image resource available
+ inside a .ICO file (Windows Icon format).
+ */
+void Fl_ICO_Image::load_ico_(Fl_Image_Reader &rdr, int id)
+{
+  int pickedID = -1;
+
+  // Check file header (ICONDIR, 6 bytes)
+
+  if (rdr.read_word() != 0 || rdr.read_word() != 1) {
+    Fl::error("Fl_ICO_Image: %s is not an ICO file.\n", rdr.name());
+    ld(ERR_FORMAT);
+    return;
+  }
+
+  idcount_ = rdr.read_word();
+
+  if (idcount() == 0) {
+    Fl::error("Fl_ICO_Image: %s - no image resources found\n", rdr.name());
+    ld(ERR_FORMAT);
+    return;
+  }
+
+
+  // read entries (IconDirEntry, 16 bytes each)
+
+  icondirentry_ = new IconDirEntry[idcount()];
+
+  for (int i = 0; i < idcount(); ++i) {
+    icondirentry_[i].bWidth = (int)rdr.read_byte();
+    icondirentry_[i].bHeight = (int)rdr.read_byte();
+    icondirentry_[i].bColorCount = (int)rdr.read_byte();
+    icondirentry_[i].bReserved = (int)rdr.read_byte();
+    icondirentry_[i].wPlanes = (int)rdr.read_word();
+    icondirentry_[i].wBitCount = (int)rdr.read_word();
+    icondirentry_[i].dwBytesInRes = (int)rdr.read_dword();
+    icondirentry_[i].dwImageOffset = (int)rdr.read_dword();
+
+    if (icondirentry_[i].bWidth == 0) icondirentry_[i].bWidth = 256;
+    if (icondirentry_[i].bHeight == 0) icondirentry_[i].bHeight = 256;
+  }
+
+  if (id <= -2) return;
+
+  if (!icondirentry_ || idcount() < 1 || id >= idcount()) {
+    ld(ERR_FORMAT);
+    return;
+  }
+
+  if (id == -1) {
+    // pick icon with highest resolution + highest bitcount
+    int highestRes = 0, bitcount = 0;
+    for (int i = 0; i < idcount(); ++i) {
+      int res = icondirentry_[i].bWidth * icondirentry_[i].bHeight;
+      if (res > highestRes || (res == highestRes && icondirentry_[i].wBitCount > bitcount)) {
+        highestRes = res;
+        bitcount = icondirentry_[i].wBitCount;
+        pickedID = i;
+      }
+    }
+  } else {
+    pickedID = id;
+  }
+
+  if (pickedID < 0 ||
+      icondirentry_[pickedID].bWidth <= 0 ||
+      icondirentry_[pickedID].bHeight <= 0 ||
+      icondirentry_[pickedID].dwImageOffset <= 0||
+      icondirentry_[pickedID].dwBytesInRes <= 0)
+  {
+    ld(ERR_FORMAT);
+    return;
+  }
+
+  rdr.seek(icondirentry_[pickedID].dwImageOffset);
+
+
+  // Check for a PNG image resource
+  uchar b[8];
+  for (int i=0; i<8; ++i) b[i] = rdr.read_byte();
+
+  if (b[0]==0x89 && b[1]=='P' && b[2]=='N' && b[3]=='G' &&
+      b[4]=='\r' && b[5]=='\n' && b[6]==0x1A && b[7]=='\n')
+  {
+#if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
+    Fl_PNG_Image *png = new Fl_PNG_Image(rdr.name(), icondirentry_[pickedID].dwImageOffset);
+
+    int loaded = png ? png->fail() : ERR_FILE_ACCESS;
+    if (loaded < 0) {
+      w(0); h(0); d(0);
+      ld(loaded);
+      if (png) delete png;
+      return;
+    }
+
+    w(png->w());
+    h(png->h());
+    d(png->d());
+
+    // take over pointer of Fl_PNG_Image's array
+    array = png->array;
+    alloc_array = 1;
+    png->array = NULL;
+    png->alloc_array = 0;
+
+    delete png;
+    return;
+#else
+    Fl::error("Fl_ICO_Image: %s - cannot decode PNG resource (no libpng support)!\n", rdr.name());
+    w(0); h(0); d(0);
+    ld(ERR_FORMAT);
+    return;
+#endif
+  }
+
+
+  // Bitmap resource
+
+  w(icondirentry_[pickedID].bWidth);
+  h(icondirentry_[pickedID].bHeight);
+  d(4);
+
+  if (((size_t)w()) * h() * d() > max_size()) {
+    Fl::warning("ICO file \"%s\" is too large!\n", rdr.name());
+    w(0); h(0); d(0);
+    ld(ERR_FORMAT);
+    return;
+  }
+
+  rdr.seek(icondirentry_[pickedID].dwImageOffset);
+  load_bmp_(rdr, h(), w());
+}

src/Fl_PNG_Image.cxx

@@ -4,7 +4,7 @@
 // Copyright 1997-2012 by Easy Software Products.
 // Image support by Matthias Melcher, Copyright 2000-2009.
 //
-// Copyright 2013-2021 by Bill Spitzak and others.
+// Copyright 2013-2022 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -87,9 +87,15 @@ extern "C" {
  */
 Fl_PNG_Image::Fl_PNG_Image (const char *filename): Fl_RGB_Image(0,0,0)
 {
-  load_png_(filename, NULL, 0);
+  load_png_(filename, 0, NULL, 0);
 }
 
+// private c'tor used by Fl_ICO_Image
+// \param     offset      Offset to seek for the begin of PNG data inside a .ICO file
+Fl_PNG_Image::Fl_PNG_Image (const char *filename, int offset): Fl_RGB_Image(0,0,0)
+{
+  load_png_(filename, offset, NULL, 0);
+}
 
 /**
  \brief Constructor that reads a PNG image from memory.
@@ -106,11 +112,11 @@ Fl_PNG_Image::Fl_PNG_Image (const char *filename): Fl_RGB_Image(0,0,0)
 Fl_PNG_Image::Fl_PNG_Image (
       const char *name_png, const unsigned char *buffer, int maxsize): Fl_RGB_Image(0,0,0)
 {
-  load_png_(name_png, buffer, maxsize);
+  load_png_(name_png, 0, buffer, maxsize);
 }
 
 
-void Fl_PNG_Image::load_png_(const char *name_png, const unsigned char *buffer_png, int maxsize)
+void Fl_PNG_Image::load_png_(const char *name_png, int offset, const unsigned char *buffer_png, int maxsize)
 {
 #if defined(HAVE_LIBPNG) && defined(HAVE_LIBZ)
   int i;                // Looping var
@@ -134,6 +140,12 @@ void Fl_PNG_Image::load_png_(const char *name_png, const unsigned char *buffer_p
       delete fp;
       return;
     }
+    if (offset > 0 && fseek(*fp, (long)offset, SEEK_SET) == -1) {
+      fclose(*fp);
+      ld(ERR_FORMAT);
+      delete fp;
+      return;
+    }
   }
   const char *display_name = (name_png ? name_png : "In-memory PNG data");
 

src/Makefile

@@ -228,6 +228,7 @@ IMGCPPFILES = \
 	Fl_File_Icon2.cxx \
 	Fl_GIF_Image.cxx \
 	Fl_Help_Dialog.cxx \
+	Fl_ICO_Image.cxx \
 	Fl_JPEG_Image.cxx \
 	Fl_PNG_Image.cxx \
 	Fl_PNM_Image.cxx \

src/fl_images_core.cxx

@@ -2,7 +2,7 @@
 // FLTK images library core.
 //
 // Copyright 1997-2010 by Easy Software Products.
-// Copyright 2011-2021 by Bill Spitzak and others.
+// Copyright 2011-2022 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -31,6 +31,7 @@
 #include <FL/Fl_PNG_Image.H>
 #include <FL/Fl_PNM_Image.H>
 #include <FL/Fl_SVG_Image.H>
+#include <FL/Fl_ICO_Image.H>
 #include <FL/fl_utf8.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -95,6 +96,9 @@ fl_check_images(const char *name,               // I - Filename
   if (memcmp(header, "BM", 2) == 0)     // BMP file
     return new Fl_BMP_Image(name);
 
+  if (memcmp(header, "\0\0\1\0", 4) == 0 && header[5] == 0)   // ICO file
+    return new Fl_ICO_Image(name);
+
   // PNM
 
   if (header[0] == 'P' && header[1] >= '1' && header[1] <= '7')

test/pixmap_browser.cxx

@@ -1,7 +1,7 @@
 //
 // A shared image test program for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2015 by Bill Spitzak and others.
+// Copyright 1998-2022 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -77,7 +77,7 @@ void file_cb(const char *n) {
 
 void button_cb(Fl_Widget *,void *) {
   fl_file_chooser_callback(file_cb);
-  const char *fname = fl_file_chooser("Image file?","*.{bm,bmp,gif,jpg,pbm,pgm,png,ppm,xbm,xpm"
+  const char *fname = fl_file_chooser("Image file?","*.{bm,bmp,gif,ico,jpg,pbm,pgm,png,ppm,xbm,xpm"
 #ifdef FLTK_USE_SVG
                                       ",svg"
 #ifdef HAVE_LIBZ