返回指定bitmap图片的尺寸代码,Delphi代码库,德仔网

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【Delphi】返回指定bitmap图片的尺寸

作者:jellyvice / 发布于2013-12-3/ 354

function GetBMPSize(const FileName: string): Types.TSize;
type
 // Union of two different versions of windows bitmap info records
 TBitmapInfo = packed record
  case Byte of
   0: (Core: Windows.TBitmapCoreHeader); // early version
   1: (Ext: Windows.TBitmapInfoHeader); // later version
 end;
const
 cSignature = $4D42; // bitmap file signature
var
 FileHeader: Windows.TBitmapFileHeader; // bmp file header record
 BmpInfo: TBitmapInfo;          // bmp info record union
 FS: Classes.TFileStream;        // stream onto bmp file
 BytesRead: Integer;           // bytes read from stream
begin
 Result.cx := 0;
 Result.cy := 0;
 if (FileName = '') or not SysUtils.FileExists(FileName) then
  Exit;
 FS := Classes.TFileStream.Create(
  FileName, SysUtils.fmOpenRead or SysUtils.fmShareDenyNone
 );
 try
  // Read file header and check signature
  BytesRead := FS.Read(FileHeader, SizeOf(FileHeader));
  if BytesRead <> SizeOf(FileHeader) then
   Exit;
  if FileHeader.bfType <> cSignature then
   Exit;
  // Read bitmap info record (varies according to bmp type)
  BytesRead := FS.Read(BmpInfo, SizeOf(BmpInfo));
  if BytesRead < SizeOf(DWORD) then
   Exit; // couldn't read length field
  if BytesRead < Integer(BmpInfo.Ext.biSize) then
   Exit; // couldn't read whole info header record
  if BmpInfo.Ext.biSize = SizeOf(BmpInfo.Ext) then
  begin
   // later version
   Result.cx := BmpInfo.Ext.biWidth;
   Result.cy := BmpInfo.Ext.biHeight;
  end
  else
  begin
   // early version
   Result.cx := BmpInfo.Core.bcWidth;
   Result.cy := BmpInfo.Core.bcHeight;
  end;
 finally
  FS.Free;
 end;
end;

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