delphi 从流(jpeg流,png流)到Timage 的显示方法

本文介绍如何使用Delphi中的TJpegImage和TPngImage组件从内存流加载JPEG和PNG图像,并将这些图像显示到TImage组件中。通过创建TMemoryStream实例并写入图像数据,然后设置流位置并利用TJpegImage和TPngImage的LoadFromStream方法加载图像。

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uses jpeg,pngimage

 


  jpg: TJpegImage;
  S: TStream;
  PngBit: TPngImage;

  img1: TImage;

    SetLength(A,流长度);
    S := TMemoryStream.Create;
    strCount := I;
    S.Write(A[0],strCount);
    S.Position := 0;//这一句是相当重要
    jpg := TJpegImage.Create;
    jpg.LoadFromStream(S);
    img1.Picture.Assign( jpg );


  PngBit := TPngImage.Create;
  PngBit.LoadFromStream(S);
  img1.Picture.Assign( PngBit );

procedure BitmapFileToPNG(const Source, Dest: String); var Bitmap: TBitmap; PNG: TPNGObject; begin Bitmap := TBitmap.Create; PNG := TPNGObject.Create; {In case something goes wrong, free booth Bitmap and PNG} try Bitmap.LoadFromFile(Source); PNG.Assign(Bitmap); //Convert data into png PNG.SaveToFile(Dest); finally Bitmap.Free; PNG.Free; end end; Converting from PNG file to Windows bitmap file The above inverse. Loads a png and saves into a bitmap procedure PNGFileToBitmap(const Source, Dest: String); var Bitmap: TBitmap; PNG: TPNGObject; begin PNG := TPNGObject.Create; Bitmap := TBitmap.Create; {In case something goes wrong, free booth PNG and Bitmap} try PNG.LoadFromFile(Source); Bitmap.Assign(PNG); //Convert data into bitmap Bitmap.SaveToFile(Dest); finally PNG.Free; Bitmap.Free; end end; Converting from TImage to PNG file This method converts from TImage to PNG. It has full exception handling and allows converting from file formats other than TBitmap (since they allow assigning to a TBitmap) procedure TImageToPNG(Source: TImage; const Dest: String); var PNG: TPNGObject; BMP: TBitmap; begin PNG := TPNGObject.Create; {In case something goes wrong, free PNG} try //If the TImage contains a TBitmap, just assign from it if Source.Picture.Graphic is TBitmap then PNG.Assign(TBitmap(Source.Picture.Graphic)) //Convert bitmap data into png else begin //Otherwise try to assign first to a TBimap BMP := TBitmap.Create; try BMP.Assign(Source.Picture.Graphic); PNG.Assign(BMP); finally BMP.Free; end; end; //Save to PNG format PNG.SaveToFile(Dest); finally PNG.Free; end end;
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