问题来源：
在这种情况下，图标是多尺寸图标文件这一事实并不重要。图标的位图信息标头在内部以不同于应有的方式读取。您的图标是 PNG 格式的文件图标，并且没有位图信息标题结构。之所以会出现Out of system resources 异常，是因为内部使用的过程期望图标具有TBitmapInfoHeader 结构，然后尝试根据此标头信息创建一个临时位图。对于您的图标，它是这样写的：
如果您仔细查看标题值，您会计算出系统将尝试创建一个大小为 169478669 * 218103808 像素、每像素 21060 B 的位图，至少需要 778.5 EB (exabytes)可用内存:-)
解决方法：
这当然是不可能的（此时 :-) 只是因为 PNG 文件格式图标没有此位图标题，而是在该位置直接包含 PNG 图像。解决此问题的方法是检查图像数据的前 8 个字节上是否有 PNG signature，它实际上检查是否有 PNG 图像，如果有，则将其视为 PNG 图像，否则尝试添加该图标通过TIcon 对象的常用方式。
在下面的代码中，ImageListAddIconEx 函数迭代图标文件中的所有图标，当有一个与图像列表尺寸匹配时，它会被处理。处理首先检查这 8 个字节是否在数据偏移位置上有 PNG 图像，如果有，则将此 PNG 图像添加到图像列表中。如果没有，则通过TIcon 对象以常用方式添加图标。如果成功，此函数返回图像列表中添加图标的索引，否则返回-1：
uses
PNGImage;
type
TIconDirEntry = packed record
bWidth: Byte; // image width, in pixels
bHeight: Byte; // image height, in pixels
bColorCount: Byte; // number of colors in the image (0 if >= 8bpp)
bReserved: Byte; // reserved (must be 0)
wPlanes: Word; // color planes
wBitCount: Word; // bits per pixel
dwBytesInRes: DWORD; // image data size
dwImageOffset: DWORD; // image data offset
end;
TIconDir = packed record
idReserved: Word; // reserved (must be 0)
idType: Word; // resource type (1 for icons)
idCount: Word; // image count
idEntries: array[0..255] of TIconDirEntry;
end;
PIconDir = ^TIconDir;
function ImageListAddIconEx(AImageList: TCustomImageList;
AIconStream: TMemoryStream): Integer;
var
I: Integer;
Data: PByte;
Icon: TIcon;
IconHeader: PIconDir;
Bitmap: TBitmap;
PNGImage: TPNGImage;
PNGStream: TMemoryStream;
const
PNGSignature: array[0..7] of Byte = ($89, $50, $4E, $47, $0D, $0A, $1A, $0A);
begin
// initialize result to -1
Result := -1;
// point to the icon header
IconHeader := AIconStream.Memory;
// iterate all the icons in the icon file
for I := 0 to IconHeader.idCount - 1 do
begin
// if the icon dimensions matches to the image list, then...
if (IconHeader.idEntries[I].bWidth = AImageList.Width) and
(IconHeader.idEntries[I].bHeight = AImageList.Height) then
begin
// point to the stream beginning
Data := AIconStream.Memory;
// point with the Data pointer to the current icon image data
Inc(Data, IconHeader.idEntries[I].dwImageOffset);
// check if the first 8 bytes are PNG image signature; if so, then...
if CompareMem(Data, @PNGSignature[0], 8) then
begin
Bitmap := TBitmap.Create;
try
PNGImage := TPNGImage.Create;
try
PNGStream := TMemoryStream.Create;
try
// set the icon stream position to the current icon data offset
AIconStream.Position := IconHeader.idEntries[I].dwImageOffset;
// copy the whole PNG image from icon data to a temporary stream
PNGStream.CopyFrom(AIconStream,
IconHeader.idEntries[I].dwBytesInRes);
// reset the temporary stream position to the beginning
PNGStream.Position := 0;
// load the temporary stream data to a temporary TPNGImage object
PNGImage.LoadFromStream(PNGStream);
finally
PNGStream.Free;
end;
// assign temporary TPNGImage object to a temporary TBitmap object
Bitmap.Assign(PNGImage);
finally
PNGImage.Free;
end;
// to properly add the bitmap to the image list set the AlphaFormat
// to afIgnored, see e.g. http://stackoverflow.com/a/4618630/960757
// if you don't have TBitmap.AlphaFormat property available, simply
// comment out the following line
Bitmap.AlphaFormat := afIgnored;
// and finally add the temporary TBitmap object to the image list
Result := AImageList.Add(Bitmap, nil);
finally
Bitmap.Free;
end;
end
// the icon is not PNG type icon, so load it to a TIcon object
else
begin
// reset the position of the input stream
AIconStream.Position := 0;
// load the icon and add it to the image list in a common way
Icon := TIcon.Create;
try
Icon.LoadFromStream(AIconStream);
Result := AImageList.AddIcon(Icon);
finally
Icon.Free;
end;
end;
// break the loop to exit the function
Break;
end;
end;
end;
及用法：
procedure TForm1.Button1Click(Sender: TObject);
var
Index: Integer;
Stream: TMemoryStream;
begin
Stream := TMemoryStream.Create;
try
Stream.LoadFromFile('d:\Icon.ico');
Index := ImageListAddIconEx(ImageList1, Stream);
if (Index <> -1) then
ImageList1.Draw(Canvas, 8, 8, Index);
finally
Stream.Free;
end;
end;
结论：
如果 Microsoft 推荐使用 PNG 图标格式（自 Windows Vista 起支持），则可以更新 Graphics.pas 中的 ReadIcon 过程以考虑到这一点。
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