blob: 94a77bb5cb7fe23dadfae8dcb25478c5be26679d [file] [log] [blame]
// Copyright (c) 2012 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.
#include "ui/gfx/icon_util.h"
#include "base/files/file_util.h"
#include "base/files/important_file_writer.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/win/resource_util.h"
#include "base/win/scoped_gdi_object.h"
#include "base/win/scoped_handle.h"
#include "base/win/scoped_hdc.h"
#include "skia/ext/image_operations.h"
#include "third_party/skia/include/core/SkBitmap.h"
#include "ui/gfx/gdi_util.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gfx/image/image.h"
#include "ui/gfx/image/image_family.h"
namespace {
struct ScopedICONINFO : ICONINFO {
ScopedICONINFO() {
hbmColor = NULL;
hbmMask = NULL;
~ScopedICONINFO() {
if (hbmColor)
if (hbmMask)
// Creates a new ImageFamily, |resized_image_family|, based on the images in
// |image_family|, but containing images of specific dimensions desirable for
// Windows icons. For each desired image dimension, it chooses the most
// appropriate image for that size, and resizes it to the desired size.
// Returns true on success, false on failure. Failure can occur if
// |image_family| is empty, all images in the family have size 0x0, or an image
// has no allocated pixel data.
// |resized_image_family| must be empty.
bool BuildResizedImageFamily(const gfx::ImageFamily& image_family,
gfx::ImageFamily* resized_image_family) {
for (size_t i = 0; i < IconUtil::kNumIconDimensions; ++i) {
int dimension = IconUtil::kIconDimensions[i];
gfx::Size size(dimension, dimension);
const gfx::Image* best = image_family.GetBest(size);
if (!best || best->IsEmpty()) {
// Either |image_family| is empty, or all images have size 0x0.
return false;
// Optimize for the "Large icons" view in Windows Vista+. This view displays
// icons at full size if only if there is a 256x256 (kLargeIconSize) image
// in the .ico file. Otherwise, it shrinks icons to 48x48 (kMediumIconSize).
if (dimension > IconUtil::kMediumIconSize &&
best->Width() <= IconUtil::kMediumIconSize &&
best->Height() <= IconUtil::kMediumIconSize) {
// There is no source icon larger than 48x48, so do not create any
// images larger than 48x48. kIconDimensions is sorted in ascending
// order, so it is safe to break here.
if (best->Size() == size) {
} else {
// There is no |dimension|x|dimension| source image.
// Resize this one to the desired size, and insert it.
SkBitmap best_bitmap = best->AsBitmap();
// Only kARGB_8888 images are supported.
// This will also filter out images with no pixels.
if (best_bitmap.colorType() != kN32_SkColorType)
return false;
SkBitmap resized_bitmap = skia::ImageOperations::Resize(
best_bitmap, skia::ImageOperations::RESIZE_LANCZOS3,
dimension, dimension);
return true;
// Creates a set of bitmaps from an image family.
// All images smaller than 256x256 are converted to SkBitmaps, and inserted into
// |bitmaps| in order of aspect ratio (thinnest to widest), and then ascending
// size order. If an image of exactly 256x256 is specified, it is converted into
// PNG format and stored in |png_bytes|. Images with width or height larger than
// 256 are ignored.
// |bitmaps| must be an empty vector, and not NULL.
// Returns true on success, false on failure. This fails if any image in
// |image_family| is not a 32-bit ARGB image, or is otherwise invalid.
bool ConvertImageFamilyToBitmaps(
const gfx::ImageFamily& image_family,
std::vector<SkBitmap>* bitmaps,
scoped_refptr<base::RefCountedMemory>* png_bytes) {
DCHECK(bitmaps != NULL);
for (gfx::ImageFamily::const_iterator it = image_family.begin();
it != image_family.end(); ++it) {
const gfx::Image& image = *it;
// All images should have one of the kIconDimensions sizes.
DCHECK_GT(image.Width(), 0);
DCHECK_LE(image.Width(), IconUtil::kLargeIconSize);
DCHECK_GT(image.Height(), 0);
DCHECK_LE(image.Height(), IconUtil::kLargeIconSize);
SkBitmap bitmap = image.AsBitmap();
// Only 32 bit ARGB bitmaps are supported. We also make sure the bitmap has
// been properly initialized.
SkAutoLockPixels bitmap_lock(bitmap);
if ((bitmap.colorType() != kN32_SkColorType) ||
(bitmap.getPixels() == NULL)) {
return false;
// Special case: Icons exactly 256x256 are stored in PNG format.
if (image.Width() == IconUtil::kLargeIconSize &&
image.Height() == IconUtil::kLargeIconSize) {
*png_bytes = image.As1xPNGBytes();
} else {
return true;
} // namespace
// The icon images appear in the icon file in same order in which their
// corresponding dimensions appear in this array, so it is important to keep
// this array sorted. Also note that the maximum icon image size we can handle
// is 256 by 256. See:
const int IconUtil::kIconDimensions[] = {
8, // Recommended by the MSDN as a nice to have icon size.
10, // Used by the Shell (e.g. for shortcuts).
14, // Recommended by the MSDN as a nice to have icon size.
16, // Toolbar, Application and Shell icon sizes.
22, // Recommended by the MSDN as a nice to have icon size.
24, // Used by the Shell (e.g. for shortcuts).
32, // Toolbar, Dialog and Wizard icon size.
40, // Quick Launch.
48, // Alt+Tab icon size.
64, // Recommended by the MSDN as a nice to have icon size.
96, // Recommended by the MSDN as a nice to have icon size.
128, // Used by the Shell (e.g. for shortcuts).
256 // Used by Vista onwards for large icons.
const size_t IconUtil::kNumIconDimensions = arraysize(kIconDimensions);
const size_t IconUtil::kNumIconDimensionsUpToMediumSize = 9;
HICON IconUtil::CreateHICONFromSkBitmap(const SkBitmap& bitmap) {
// Only 32 bit ARGB bitmaps are supported. We also try to perform as many
// validations as we can on the bitmap.
SkAutoLockPixels bitmap_lock(bitmap);
if ((bitmap.colorType() != kN32_SkColorType) ||
(bitmap.width() <= 0) || (bitmap.height() <= 0) ||
(bitmap.getPixels() == NULL))
return NULL;
// We start by creating a DIB which we'll use later on in order to create
// the HICON. We use BITMAPV5HEADER since the bitmap we are about to convert
// may contain an alpha channel and the V5 header allows us to specify the
// alpha mask for the DIB.
BITMAPV5HEADER bitmap_header;
InitializeBitmapHeader(&bitmap_header, bitmap.width(), bitmap.height());
void* bits = NULL;
base::win::ScopedGetDC hdc(NULL);
dib = ::CreateDIBSection(hdc, reinterpret_cast<BITMAPINFO*>(&bitmap_header),
DIB_RGB_COLORS, &bits, NULL, 0);
if (!dib || !bits)
return NULL;
memcpy(bits, bitmap.getPixels(), bitmap.width() * bitmap.height() * 4);
// Icons are generally created using an AND and XOR masks where the AND
// specifies boolean transparency (the pixel is either opaque or
// transparent) and the XOR mask contains the actual image pixels. If the XOR
// mask bitmap has an alpha channel, the AND monochrome bitmap won't
// actually be used for computing the pixel transparency. Even though all our
// bitmap has an alpha channel, Windows might not agree when all alpha values
// are zero. So the monochrome bitmap is created with all pixels transparent
// for this case. Otherwise, it is created with all pixels opaque.
bool bitmap_has_alpha_channel = PixelsHaveAlpha(
static_cast<const uint32*>(bitmap.getPixels()),
bitmap.width() * bitmap.height());
scoped_ptr<uint8[]> mask_bits;
if (!bitmap_has_alpha_channel) {
// Bytes per line with paddings to make it word alignment.
size_t bytes_per_line = (bitmap.width() + 0xF) / 16 * 2;
size_t mask_bits_size = bytes_per_line * bitmap.height();
mask_bits.reset(new uint8[mask_bits_size]);
// Make all pixels transparent.
memset(mask_bits.get(), 0xFF, mask_bits_size);
HBITMAP mono_bitmap = ::CreateBitmap(bitmap.width(), bitmap.height(), 1, 1,
ICONINFO icon_info;
icon_info.fIcon = TRUE;
icon_info.xHotspot = 0;
icon_info.yHotspot = 0;
icon_info.hbmMask = mono_bitmap;
icon_info.hbmColor = dib;
HICON icon = ::CreateIconIndirect(&icon_info);
return icon;
SkBitmap* IconUtil::CreateSkBitmapFromHICON(HICON icon, const gfx::Size& s) {
// We start with validating parameters.
if (!icon || s.IsEmpty())
return NULL;
ScopedICONINFO icon_info;
if (!::GetIconInfo(icon, &icon_info))
return NULL;
if (!icon_info.fIcon)
return NULL;
return new SkBitmap(CreateSkBitmapFromHICONHelper(icon, s));
scoped_ptr<SkBitmap> IconUtil::CreateSkBitmapFromIconResource(HMODULE module,
int resource_id,
int size) {
DCHECK_LE(size, kLargeIconSize);
// For everything except the Vista+ 256x256 icons, use |LoadImage()|.
if (size != kLargeIconSize) {
HICON icon_handle =
static_cast<HICON>(LoadImage(module, MAKEINTRESOURCE(resource_id),
IMAGE_ICON, size, size,
scoped_ptr<SkBitmap> bitmap(IconUtil::CreateSkBitmapFromHICON(icon_handle));
return bitmap.Pass();
// For Vista+ 256x256 PNG icons, read the resource directly and find
// the corresponding icon entry to get its PNG bytes.
void* icon_dir_data = NULL;
size_t icon_dir_size = 0;
if (!base::win::GetResourceFromModule(module, resource_id, RT_GROUP_ICON,
&icon_dir_data, &icon_dir_size)) {
return nullptr;
DCHECK_GE(icon_dir_size, sizeof(GRPICONDIR));
const GRPICONDIR* icon_dir =
reinterpret_cast<const GRPICONDIR*>(icon_dir_data);
const GRPICONDIRENTRY* large_icon_entry = NULL;
for (size_t i = 0; i < icon_dir->idCount; ++i) {
const GRPICONDIRENTRY* entry = &icon_dir->idEntries[i];
// 256x256 icons are stored with width and height set to 0.
// See:
if (entry->bWidth == 0 && entry->bHeight == 0) {
large_icon_entry = entry;
if (!large_icon_entry)
return nullptr;
void* png_data = NULL;
size_t png_size = 0;
if (!base::win::GetResourceFromModule(module, large_icon_entry->nID, RT_ICON,
&png_data, &png_size)) {
return nullptr;
DCHECK_EQ(png_size, large_icon_entry->dwBytesInRes);
gfx::Image image = gfx::Image::CreateFrom1xPNGBytes(
new base::RefCountedStaticMemory(png_data, png_size));
return make_scoped_ptr(new SkBitmap(image.AsBitmap()));
SkBitmap* IconUtil::CreateSkBitmapFromHICON(HICON icon) {
// We start with validating parameters.
if (!icon)
return NULL;
ScopedICONINFO icon_info;
BITMAP bitmap_info = { 0 };
if (!::GetIconInfo(icon, &icon_info))
return NULL;
if (!::GetObject(icon_info.hbmMask, sizeof(bitmap_info), &bitmap_info))
return NULL;
gfx::Size icon_size(bitmap_info.bmWidth, bitmap_info.bmHeight);
return new SkBitmap(CreateSkBitmapFromHICONHelper(icon, icon_size));
HICON IconUtil::CreateCursorFromDIB(const gfx::Size& icon_size,
const gfx::Point& hotspot,
const void* dib_bits,
size_t dib_size) {
BITMAPINFO icon_bitmap_info = {};
base::win::ScopedGetDC dc(NULL);
base::win::ScopedCreateDC working_dc(CreateCompatibleDC(dc));
base::win::ScopedGDIObject<HBITMAP> bitmap_handle(
if (dib_size > 0) {
HBITMAP old_bitmap = reinterpret_cast<HBITMAP>(
SelectObject(working_dc.Get(), bitmap_handle));
SetBkMode(working_dc.Get(), TRANSPARENT);
SelectObject(working_dc.Get(), old_bitmap);
base::win::ScopedGDIObject<HBITMAP> mask(
ICONINFO ii = {0};
ii.fIcon = FALSE;
ii.xHotspot = hotspot.x();
ii.yHotspot = hotspot.y();
ii.hbmMask = mask;
ii.hbmColor = bitmap_handle;
return CreateIconIndirect(&ii);
SkBitmap IconUtil::CreateSkBitmapFromHICONHelper(HICON icon,
const gfx::Size& s) {
// Allocating memory for the SkBitmap object. We are going to create an ARGB
// bitmap so we should set the configuration appropriately.
SkBitmap bitmap;
bitmap.allocN32Pixels(s.width(), s.height());
bitmap.eraseARGB(0, 0, 0, 0);
SkAutoLockPixels bitmap_lock(bitmap);
// Now we should create a DIB so that we can use ::DrawIconEx in order to
// obtain the icon's image.
InitializeBitmapHeader(&h, s.width(), s.height());
HDC hdc = ::GetDC(NULL);
uint32* bits;
HBITMAP dib = ::CreateDIBSection(hdc, reinterpret_cast<BITMAPINFO*>(&h),
DIB_RGB_COLORS, reinterpret_cast<void**>(&bits), NULL, 0);
HDC dib_dc = CreateCompatibleDC(hdc);
::ReleaseDC(NULL, hdc);
HGDIOBJ old_obj = ::SelectObject(dib_dc, dib);
// Windows icons are defined using two different masks. The XOR mask, which
// represents the icon image and an AND mask which is a monochrome bitmap
// which indicates the transparency of each pixel.
// To make things more complex, the icon image itself can be an ARGB bitmap
// and therefore contain an alpha channel which specifies the transparency
// for each pixel. Unfortunately, there is no easy way to determine whether
// or not a bitmap has an alpha channel and therefore constructing the bitmap
// for the icon is nothing but straightforward.
// The idea is to read the AND mask but use it only if we know for sure that
// the icon image does not have an alpha channel. The only way to tell if the
// bitmap has an alpha channel is by looking through the pixels and checking
// whether there are non-zero alpha bytes.
// We start by drawing the AND mask into our DIB.
size_t num_pixels = s.GetArea();
memset(bits, 0, num_pixels * 4);
::DrawIconEx(dib_dc, 0, 0, icon, s.width(), s.height(), 0, NULL, DI_MASK);
// Capture boolean opacity. We may not use it if we find out the bitmap has
// an alpha channel.
scoped_ptr<bool[]> opaque(new bool[num_pixels]);
for (size_t i = 0; i < num_pixels; ++i)
opaque[i] = !bits[i];
// Then draw the image itself which is really the XOR mask.
memset(bits, 0, num_pixels * 4);
::DrawIconEx(dib_dc, 0, 0, icon, s.width(), s.height(), 0, NULL, DI_NORMAL);
memcpy(bitmap.getPixels(), static_cast<void*>(bits), num_pixels * 4);
// Finding out whether the bitmap has an alpha channel.
bool bitmap_has_alpha_channel = PixelsHaveAlpha(
static_cast<const uint32*>(bitmap.getPixels()), num_pixels);
// If the bitmap does not have an alpha channel, we need to build it using
// the previously captured AND mask. Otherwise, we are done.
if (!bitmap_has_alpha_channel) {
uint32* p = static_cast<uint32*>(bitmap.getPixels());
for (size_t i = 0; i < num_pixels; ++p, ++i) {
DCHECK_EQ((*p & 0xff000000), 0u);
if (opaque[i])
*p |= 0xff000000;
*p &= 0x00ffffff;
::SelectObject(dib_dc, old_obj);
return bitmap;
// static
bool IconUtil::CreateIconFileFromImageFamily(
const gfx::ImageFamily& image_family,
const base::FilePath& icon_path) {
// Creating a set of bitmaps corresponding to the icon images we'll end up
// storing in the icon file. Each bitmap is created by resizing the most
// appropriate image from |image_family| to the desired size.
gfx::ImageFamily resized_image_family;
if (!BuildResizedImageFamily(image_family, &resized_image_family))
return false;
std::vector<SkBitmap> bitmaps;
scoped_refptr<base::RefCountedMemory> png_bytes;
if (!ConvertImageFamilyToBitmaps(resized_image_family, &bitmaps, &png_bytes))
return false;
// Guaranteed true because BuildResizedImageFamily will provide at least one
// image < 256x256.
size_t bitmap_count = bitmaps.size(); // Not including PNG image.
// Including PNG image, if any.
size_t image_count = bitmap_count + (png_bytes.get() ? 1 : 0);
// Computing the total size of the buffer we need in order to store the
// images in the desired icon format.
size_t buffer_size = ComputeIconFileBufferSize(bitmaps);
// Account for the bytes needed for the PNG entry.
if (png_bytes.get())
buffer_size += sizeof(ICONDIRENTRY) + png_bytes->size();
// Setting the information in the structures residing within the buffer.
// First, we set the information which doesn't require iterating through the
// bitmap set and then we set the bitmap specific structures. In the latter
// step we also copy the actual bits.
std::vector<uint8> buffer(buffer_size);
ICONDIR* icon_dir = reinterpret_cast<ICONDIR*>(&buffer[0]);
icon_dir->idType = kResourceTypeIcon;
icon_dir->idCount = static_cast<WORD>(image_count);
// - 1 because there is already one ICONDIRENTRY in ICONDIR.
size_t icon_dir_count = image_count - 1;
size_t offset = sizeof(ICONDIR) + (sizeof(ICONDIRENTRY) * icon_dir_count);
for (size_t i = 0; i < bitmap_count; i++) {
ICONIMAGE* image = reinterpret_cast<ICONIMAGE*>(&buffer[offset]);
DCHECK_LT(offset, buffer_size);
size_t icon_image_size = 0;
SetSingleIconImageInformation(bitmaps[i], i, icon_dir, image, offset,
DCHECK_GT(icon_image_size, 0U);
offset += icon_image_size;
// Add the PNG entry, if necessary.
if (png_bytes.get()) {
ICONDIRENTRY* entry = &icon_dir->idEntries[bitmap_count];
entry->bWidth = 0;
entry->bHeight = 0;
entry->wPlanes = 1;
entry->wBitCount = 32;
entry->dwBytesInRes = static_cast<DWORD>(png_bytes->size());
entry->dwImageOffset = static_cast<DWORD>(offset);
memcpy(&buffer[offset], png_bytes->front(), png_bytes->size());
offset += png_bytes->size();
DCHECK_EQ(offset, buffer_size);
std::string data(buffer.begin(), buffer.end());
return base::ImportantFileWriter::WriteFileAtomically(icon_path, data);
bool IconUtil::PixelsHaveAlpha(const uint32* pixels, size_t num_pixels) {
for (const uint32* end = pixels + num_pixels; pixels != end; ++pixels) {
if ((*pixels & 0xff000000) != 0)
return true;
return false;
void IconUtil::InitializeBitmapHeader(BITMAPV5HEADER* header, int width,
int height) {
memset(header, 0, sizeof(BITMAPV5HEADER));
header->bV5Size = sizeof(BITMAPV5HEADER);
// Note that icons are created using top-down DIBs so we must negate the
// value used for the icon's height.
header->bV5Width = width;
header->bV5Height = -height;
header->bV5Planes = 1;
header->bV5Compression = BI_RGB;
// Initializing the bitmap format to 32 bit ARGB.
header->bV5BitCount = 32;
header->bV5RedMask = 0x00FF0000;
header->bV5GreenMask = 0x0000FF00;
header->bV5BlueMask = 0x000000FF;
header->bV5AlphaMask = 0xFF000000;
// Use the system color space. The default value is LCS_CALIBRATED_RGB, which
// causes us to crash if we don't specify the approprite gammas, etc. See
// <> and
// <http://b/1283121>.
// Use a valid value for bV5Intent as 0 is not a valid one.
// <>
header->bV5Intent = LCS_GM_IMAGES;
void IconUtil::SetSingleIconImageInformation(const SkBitmap& bitmap,
size_t index,
ICONDIR* icon_dir,
ICONIMAGE* icon_image,
size_t image_offset,
size_t* image_byte_count) {
DCHECK(icon_dir != NULL);
DCHECK(icon_image != NULL);
DCHECK_GT(image_offset, 0U);
DCHECK(image_byte_count != NULL);
DCHECK_LT(bitmap.width(), kLargeIconSize);
DCHECK_LT(bitmap.height(), kLargeIconSize);
// We start by computing certain image values we'll use later on.
size_t xor_mask_size, bytes_in_resource;
icon_dir->idEntries[index].bWidth = static_cast<BYTE>(bitmap.width());
icon_dir->idEntries[index].bHeight = static_cast<BYTE>(bitmap.height());
icon_dir->idEntries[index].wPlanes = 1;
icon_dir->idEntries[index].wBitCount = 32;
icon_dir->idEntries[index].dwBytesInRes = bytes_in_resource;
icon_dir->idEntries[index].dwImageOffset = image_offset;
icon_image->icHeader.biSize = sizeof(BITMAPINFOHEADER);
// The width field in the BITMAPINFOHEADER structure accounts for the height
// of both the AND mask and the XOR mask so we need to multiply the bitmap's
// height by 2. The same does NOT apply to the width field.
icon_image->icHeader.biHeight = bitmap.height() * 2;
icon_image->icHeader.biWidth = bitmap.width();
icon_image->icHeader.biPlanes = 1;
icon_image->icHeader.biBitCount = 32;
// We use a helper function for copying to actual bits from the SkBitmap
// object into the appropriate space in the buffer. We use a helper function
// (rather than just copying the bits) because there is no way to specify the
// orientation (bottom-up vs. top-down) of a bitmap residing in a .ico file.
// Thus, if we just copy the bits, we'll end up with a bottom up bitmap in
// the .ico file which will result in the icon being displayed upside down.
// The helper function copies the image into the buffer one scanline at a
// time.
// Note that we don't need to initialize the AND mask since the memory
// allocated for the icon data buffer was initialized to zero. The icon we
// create will therefore use an AND mask containing only zeros, which is OK
// because the underlying image has an alpha channel. An AND mask containing
// only zeros essentially means we'll initially treat all the pixels as
// opaque.
unsigned char* image_addr = reinterpret_cast<unsigned char*>(icon_image);
unsigned char* xor_mask_addr = image_addr + sizeof(BITMAPINFOHEADER);
CopySkBitmapBitsIntoIconBuffer(bitmap, xor_mask_addr, xor_mask_size);
*image_byte_count = bytes_in_resource;
void IconUtil::CopySkBitmapBitsIntoIconBuffer(const SkBitmap& bitmap,
unsigned char* buffer,
size_t buffer_size) {
SkAutoLockPixels bitmap_lock(bitmap);
unsigned char* bitmap_ptr = static_cast<unsigned char*>(bitmap.getPixels());
size_t bitmap_size = bitmap.height() * bitmap.width() * 4;
DCHECK_EQ(buffer_size, bitmap_size);
for (size_t i = 0; i < bitmap_size; i += bitmap.width() * 4) {
memcpy(buffer + bitmap_size - bitmap.width() * 4 - i,
bitmap_ptr + i,
bitmap.width() * 4);
size_t IconUtil::ComputeIconFileBufferSize(const std::vector<SkBitmap>& set) {
// We start by counting the bytes for the structures that don't depend on the
// number of icon images. Note that sizeof(ICONDIR) already accounts for a
// single ICONDIRENTRY structure, which is why we subtract one from the
// number of bitmaps.
size_t total_buffer_size = sizeof(ICONDIR);
size_t bitmap_count = set.size();
total_buffer_size += sizeof(ICONDIRENTRY) * (bitmap_count - 1);
// May not have all icon sizes, but must have at least up to medium icon size.
DCHECK_GE(bitmap_count, kNumIconDimensionsUpToMediumSize);
// Add the bitmap specific structure sizes.
for (size_t i = 0; i < bitmap_count; i++) {
size_t xor_mask_size, bytes_in_resource;
total_buffer_size += bytes_in_resource;
return total_buffer_size;
void IconUtil::ComputeBitmapSizeComponents(const SkBitmap& bitmap,
size_t* xor_mask_size,
size_t* bytes_in_resource) {
// The XOR mask size is easy to calculate since we only deal with 32bpp
// images.
*xor_mask_size = bitmap.width() * bitmap.height() * 4;
// Computing the AND mask is a little trickier since it is a monochrome
// bitmap (regardless of the number of bits per pixels used in the XOR mask).
// There are two things we must make sure we do when computing the AND mask
// size:
// 1. Make sure the right number of bytes is allocated for each AND mask
// scan line in case the number of pixels in the image is not divisible by
// 8. For example, in a 15X15 image, 15 / 8 is one byte short of
// containing the number of bits we need in order to describe a single
// image scan line so we need to add a byte. Thus, we need 2 bytes instead
// of 1 for each scan line.
// 2. Make sure each scan line in the AND mask is 4 byte aligned (so that the
// total icon image has a 4 byte alignment). In the 15X15 image example
// above, we can not use 2 bytes so we increase it to the next multiple of
// 4 which is 4.
// Once we compute the size for a singe AND mask scan line, we multiply that
// number by the image height in order to get the total number of bytes for
// the AND mask. Thus, for a 15X15 image, we need 15 * 4 which is 60 bytes
// for the monochrome bitmap representing the AND mask.
size_t and_line_length = (bitmap.width() + 7) >> 3;
and_line_length = (and_line_length + 3) & ~3;
size_t and_mask_size = and_line_length * bitmap.height();
size_t masks_size = *xor_mask_size + and_mask_size;
*bytes_in_resource = masks_size + sizeof(BITMAPINFOHEADER);