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).

1 files changed, 202 insertions, 0 deletions

diff --git a/src/Fl_ICO_Image.cxx b/src/Fl_ICO_Image.cxx
new file mode 100644
index 000000000..9de71737b
--- /dev/null
+++ b/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());
+}