gfx/icon_util.h

// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef GFX_ICON_UTIL_H_
#define GFX_ICON_UTIL_H_

#include <windows.h>
#include <string>
#include <vector>
#include "base/basictypes.h"

namespace gfx {
  class Size;
}
class SkBitmap;

///////////////////////////////////////////////////////////////////////////////
//
// The IconUtil class contains helper functions for manipulating Windows icons.
// The class interface contains methods for converting an HICON handle into an
// SkBitmap object and vice versa. The class can also create a .ico file given
// a PNG image contained in an SkBitmap object. The following code snippet
// shows an example usage of IconUtil::CreateHICONFromSkBitmap():
//
//   SkBitmap bitmap;
//
//   // Fill |bitmap| with valid data
//   bitmap.setConfig(...);
//   bitmap.allocPixels();
//
//   ...
//
//   // Convert the bitmap into a Windows HICON
//   HICON icon = IconUtil::CreateHICONFromSkBitmap(bitmap);
//   if (icon == NULL) {
//     // Handle error
//     ...
//   }
//
//   // Use the icon with a WM_SETICON message
//   ::SendMessage(hwnd, WM_SETICON, static_cast<WPARAM>(ICON_BIG),
//                 reinterpret_cast<LPARAM>(icon));
//
//   // Destroy the icon when we are done
//   ::DestroyIcon(icon);
//
///////////////////////////////////////////////////////////////////////////////
class IconUtil {
 public:
  // Given an SkBitmap object, the function converts the bitmap to a Windows
  // icon and returns the corresponding HICON handle. If the function can not
  // convert the bitmap, NULL is returned.
  //
  // The client is responsible for destroying the icon when it is no longer
  // needed by calling ::DestroyIcon().
  static HICON CreateHICONFromSkBitmap(const SkBitmap& bitmap);

  // Given a valid HICON handle representing an icon, this function converts
  // the icon into an SkBitmap object containing an ARGB bitmap using the
  // dimensions specified in |s|. |s| must specify valid dimensions (both
  // width() an height() must be greater than zero). If the function can
  // convert the icon to a bitmap (most probably due to an invalid parameter),
  // the return value is NULL.
  //
  // The client owns the returned bitmap object and is responsible for deleting
  // it when it is no longer needed.
  static SkBitmap* CreateSkBitmapFromHICON(HICON icon, const gfx::Size& s);

  // Given an initialized SkBitmap object and a file name, this function
  // creates a .ico file with the given name using the provided bitmap. The
  // icon file is created with multiple icon images of varying predefined
  // dimensions because Windows uses different image sizes when loading icons,
  // depending on where the icon is drawn (ALT+TAB window, desktop shortcut,
  // Quick Launch, etc.). |icon_file_name| needs to specify the full path for
  // the desired .ico file.
  //
  // The function returns true on success and false otherwise.
  static bool CreateIconFileFromSkBitmap(const SkBitmap& bitmap,
                                         const std::wstring& icon_file_name);

 private:
  // The icon format is published in the MSDN but there is no definition of
  // the icon file structures in any of the Windows header files so we need to
  // define these structure within the class. We must make sure we use 2 byte
  // packing so that the structures are layed out properly within the file.
#pragma pack(push)
#pragma pack(2)

  // ICONDIRENTRY contains meta data for an individual icon image within a
  // .ico file.
  struct ICONDIRENTRY {
    BYTE bWidth;
    BYTE bHeight;
    BYTE bColorCount;
    BYTE bReserved;
    WORD wPlanes;
    WORD wBitCount;
    DWORD dwBytesInRes;
    DWORD dwImageOffset;
  };

  // ICONDIR Contains information about all the icon images contained within a
  // single .ico file.
  struct ICONDIR {
    WORD idReserved;
    WORD idType;
    WORD idCount;
    ICONDIRENTRY idEntries[1];
  };

  // Contains the actual icon image.
  struct ICONIMAGE {
    BITMAPINFOHEADER icHeader;
    RGBQUAD icColors[1];
    BYTE icXOR[1];
    BYTE icAND[1];
  };
#pragma pack(pop)

  // Used for indicating that the .ico contains an icon (rather than a cursor)
  // image. This value is set in the |idType| field of the ICONDIR structure.
  static const int kResourceTypeIcon = 1;

  // The dimensions of the icon images we insert into the .ico file.
  static const int icon_dimensions_[];

  // Returns how many icon dimensions are defined.
  static int GetIconDimensionCount();

  // Returns true if any pixel in the given pixels buffer has an non-zero alpha.
  static bool PixelsHaveAlpha(const uint32* pixels, size_t num_pixels);

  // A helper function that initializes a BITMAPV5HEADER structure with a set
  // of values.
  static void InitializeBitmapHeader(BITMAPV5HEADER* header, int width,
                                     int height);

  // Given a single SkBitmap object and pointers to the corresponding icon
  // structures within the icon data buffer, this function sets the image
  // information (dimensions, color depth, etc.) in the icon structures and
  // also copies the underlying icon image into the appropriate location.
  //
  // The function will set the data pointed to by |image_byte_count| with the
  // number of image bytes written to the buffer. Note that the number of bytes
  // includes only the image data written into the memory pointed to by
  // |icon_image|.
  static void SetSingleIconImageInformation(const SkBitmap& bitmap,
                                            int index,
                                            ICONDIR* icon_dir,
                                            ICONIMAGE* icon_image,
                                            int image_offset,
                                            int* image_byte_count);

  // Copies the bits of an SkBitmap object into a buffer holding the bits of
  // the corresponding image for an icon within the .ico file.
  static void CopySkBitmapBitsIntoIconBuffer(const SkBitmap& bitmap,
                                             unsigned char* buffer,
                                             int buffer_size);

  // Given a single bitmap, this function creates a set of bitmaps with
  // specific dimensions by resizing the given bitmap to the appropriate sizes.
  static void CreateResizedBitmapSet(const SkBitmap& bitmap_to_resize,
                                     std::vector<SkBitmap>* bitmaps);

  // Given a set of bitmaps with varying dimensions, this function computes
  // the amount of memory needed in order to store the bitmaps as image icons
  // in a .ico file.
  static int ComputeIconFileBufferSize(const std::vector<SkBitmap>& set);

  // A helper function for computing various size components of a given bitmap.
  // The different sizes can be used within the various .ico file structures.
  //
  // |xor_mask_size| - the size, in bytes, of the XOR mask in the ICONIMAGE
  //                   structure.
  // |and_mask_size| - the size, in bytes, of the AND mask in the ICONIMAGE
  //                   structure.
  // |bytes_in_resource| - the total number of bytes set in the ICONIMAGE
  //                       structure. This value is equal to the sum of the
  //                       bytes in the AND mask and the XOR mask plus the size
  //                       of the BITMAPINFOHEADER structure. Note that since
  //                       only 32bpp are handled by the IconUtil class, the
  //                       icColors field in the ICONIMAGE structure is ignored
  //                       and is not accounted for when computing the
  //                       different size components.
  static void ComputeBitmapSizeComponents(const SkBitmap& bitmap,
                                          int* xor_mask_size,
                                          int* and_mask_size,
                                          int* bytes_in_resource);

  // Prevent clients from instantiating objects of that class by declaring the
  // ctor/dtor as private.
  DISALLOW_IMPLICIT_CONSTRUCTORS(IconUtil);
};

#endif  // GFX_ICON_UTIL_H_