delphi 下载网络图片并显示

unit ufrmDownloadImageHTTP;

interface

uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, ExtCtrls, StdCtrls, IdBaseComponent, IdComponent,

  IdTCPConnection, IdTCPClient, IdHTTP, jpeg, GIFImg, vcl.Imaging.pngimage;

type

  TfrmDownloadImageHTTP = class(TForm)

    ScrollBox1: TScrollBox;

    Button1: TButton;

    Edit1: TEdit;

    Label1: TLabel;

    Image1: TImage;

    procedure Button1Click(Sender: TObject);

  private

    function DownloadImage(const Url: string ; ImageType : TGraphicClass = NIL) : TBitMap;

    { Private declarations }

  public

    { Public declarations }

  end;

var

  frmDownloadImageHTTP: TfrmDownloadImageHTTP;

implementation

{$R *.dfm}

function TfrmDownloadImageHTTP.DownloadImage(const Url: string ; ImageType : TGraphicClass = NIL) : TBitMap;

var

  Http: TIdHttp;

  S: TStream;

  Img: TGraphic;

  Str: AnsiString;

  Buff: string;

begin

  Http := TIdHTTP.Create(NIL);

  try

    S := TMemoryStream.Create;

    Buff := StringReplace(Url,'\','',[rfReplaceAll,rfIgnoreCase]);

    try

      Http.Get(Buff,S);

      if not Assigned(ImageType) then begin

        S.Position:=0;

        SetLength(STR,5);

        S.Read(STR[1],LENGTH(STR));

        if Copy(STR,1,2)='BM' then

          ImageType:=TBitMap

        else if COPY(STR,1,3)='GIF' then

          ImageType:= TGIFImage

        else if COPY(STR,2,3)='PNG' then

          ImageType:= TPNGObject

        else if (ORD(STR[1])=$FF) AND (ORD(STR[2])=$D8) then

          ImageType:=TJPEGImage

      end;

      if not Assigned(ImageType) then raise EInvalidImage.Create('Unrecognized file format!');

      IMG:=ImageType.Create;

      try

        S.Position:=0;

        IMG.LoadFromStream(S);

        Result:=TBitMap.Create;

        try

          Result.Assign(IMG)

        except

          Result.Free;

          raise;

        end;

      finally

        IMG.Free

      end;

    finally

      S.Free

    end;

  finally

    HTTP.Free

  end;

end;

procedure TfrmDownloadImageHTTP.Button1Click(Sender: TObject);

begin

  Image1.Picture.Bitmap := DownloadImage(Edit1.Text);

end;

end.