图像压缩问题！！

Question

JPG格式怎么存？
菜鸟请教了！

Answer 1

楼上的老兄呀，用jpg格式，才能压缩多少呀，我这个默认值就能压100倍！

Answer 2

unit zipfunc;
{
压缩解压单元作者：fontain 日期：2002.2.9功能：
     compressstream:从指定流中压缩内容，结果存到指定文件和原流
     uncompressfile: 从指定文件解压，结果存到指定流
使用单元：zlib,classes,Sysutils;
}
interface
uses zlib,classes,Sysutils;
Function CompressToFile(var CompressedStream: TMemoryStream;const filename:string):boolean;
function UnCompressFromFile(const filename:string;var res: TMemoryStream):boolean;
implementation
Function CompressToFile(var CompressedStream: TMemoryStream;const filename:string):boolean;
var
  SourceStream: TCompressionStream;
  DestStream: TMemoryStream;
  Count: Integer;
Begin
    //获得数据流的原始尺寸
    result:=false;
    Count := CompressedStream.Size;
    DestStream := TMemoryStream.Create;
    SourceStream:=TCompressionStream.Create(clDefault, DestStream);
    Try
      //SourceStream中保存着原始的数据流
      CompressedStream.SaveToStream(SourceStream);
      //将原始数据流进行压缩， DestStream中保存着压缩后的数据流
      SourceStream.Free;
      CompressedStream.Clear;
      //写入原始数据流尺寸
      CompressedStream.WriteBuffer(Count, SizeOf(Count));
      //写入经过压缩的数据流
      CompressedStream.CopyFrom(DestStream, 0);
      CompressedStream.SaveToFile(filename);
      result:=true;
    finally
      DestStream.Free;
    end;
end;function UnCompressFromFile(const filename: string;var res: TMemoryStream):boolean;
//解压缩文件数据流
var
  SourceStream: TDecompressionStream;
  Buffer: PChar;
  Count: Integer;
  CompressedStream:TFileStream;
Begin
  result:=false;
  //从被压缩的数据流中读出原始数据流尺寸
  CompressedStream:=TFileStream.Create(filename,fmOpenRead);
  CompressedStream.ReadBuffer(Count, SizeOf(Count));
  //根据数据流尺寸大小为将要读入的原始数据流分配内存块
  GetMem(Buffer, Count);
  SourceStream := TDecompressionStream.Create(CompressedStream);
  Try
    //将被压缩的数据流解压缩，然后存入 Buffer内存块中
    SourceStream.readBuffer(Buffer^, Count);
    //将原始数据流保存至res流中
    res.writeBuffer(Buffer^, Count);
    res.Position := 0;//复位流指针
    result:=true;
  finally
    FreeMem(Buffer);
    CompressedStream.Free;
  end;
end;end.

Answer 3

to 40Star(陪你去看--☆流星雨★) 
uses graphics,jpeg,......;
.....
var a:TBitMap;
    b:TjpegImage;
begin
    a:=TBitMap.Create;
    b:=TJpegImage.Create;
    a.LoadFromFile('e:\aa.bmp');
    b.Assign(a);
    b.SaveToFile('e:\kk.jpg');
    a.free;
    b.free;
end;

Answer 4

to: fontain
代码在exe中执行没问题但原样移植到dll就出错，各位看看怎么回事?
...
b.Assign(a);   //出错句
...