解析 png 图片的十六进制字符流

uses pngimage;  
  
{从 png 图片到十六进制字符串}  
function Png2Hex(png: TPngImage): string;  
var  
  stream: TMemoryStream;  
begin  
  stream := TMemoryStream.Create;  
  png.SaveToStream(stream);  
  SetLength(Result, stream.Size * 2);  
  BinToHex(stream.Memory, PChar(Result), stream.Size);  
  stream.Free;  
end;  
  
{从十六进制字符串恢复 png 图片}  
procedure Hex2Png(str: string; out png: TPngImage);  
var  
  stream: TMemoryStream;  
begin  
  if not Assigned(png) then png := TPngImage.Create;  
  stream := TMemoryStream.Create;  
  stream.SetSize(Length(str) div 2);  
  HexToBin(PChar(str), stream.Memory, stream.Size);  
  png.LoadFromStream(stream);  
  stream.Free;  
end;  
  
{测试}  
procedure TForm1.Button1Click(Sender: TObject);  
var  
  png: TPngImage;  
begin  
  png := TPngImage.Create;  
  png.LoadFromFile('c:/temp/test.png');  
  Memo1.Text := Png2Hex(png);  
  png.Free;  
end;  
  
procedure TForm1.Button2Click(Sender: TObject);  
var  
  png: TPngImage;  
begin  
  png := TPngImage.Create;  
  Hex2Png(Memo1.Text, png);  
  Canvas.Draw(0, 0, png);  
  png.Free;  
end;