关于图片缩放--------为什么这段代码有问题?

Question

本帖最后由 cowbobe 于 2013-11-03 22:02:05 编辑

Answer 1

//图片放大缩小
procedure ResizeBmp(SrcBM: TBitmap; zoom: Single);//<<<<
var
  rect: TRect;
  NewW, NewH, PicW, PicH: Integer;
  tem: Single;
  bmp:TBitmap;  //<<<<
begin
  PicW := SrcBM.Width;
  PicH := SrcBM.Height;
  tem := PicW;
  NewW := trunc(tem * zoom);
  tem := PicH;
  NewH := trunc(tem * zoom);  bmp:=TBitmap.Create;//<<<<
  with bmp do  //<<<<
  begin
    Width := NewW;
    Height := NewH;
    rect:= Bounds(0,0,Width,Height);//<<<<
    Canvas.StretchDraw(rect, TGraphic(SrcBM));
  end;  SrcBM.Assign(bmp); //<<<<
  bmp.Free;  //<<<<
end;//调用
procedure TMainForm.ZoomInClick(Sender: TObject);
var
    ZoomVal:Single;
begin
    ZoomVal:=ZoomVal+0.2;
    ResizeBmp(img1.Picture.Bitmap,ZoomVal); //<<<<
end;

Answer 2

注意image控件如果是通过属性面板load图片，图片就必须是bmp。
如果是通过代码动态加载图片，jpg、bmp都可以

Answer 3

调整Image的宽高，拉放设置为True不就得了……

Answer 4

请问,为什么当我先点了放大按钮几下,再点缩小的按钮动作时,还是放大动作?
procedure TMainForm.ZoomInClick(Sender: TObject);
begin
    ZoomVal:=ZoomVal+0.1;
    ResizeBmp(Image1.Picture.Bitmap,ZoomVal);
end;procedure TMainForm.ZoomOut1Click(Sender: TObject);
begin
    ZoomVal:=ZoomVal-0.1;
    ResizeBmp(Image1.Picture.Bitmap,ZoomVal);
end;

Answer 5

  var
    Bitmap : TBitmap;
    Jpg : TJPEGImage;
    WicImg: TWICImage;
    Factory: IWICImagingFactory;
    Scaler: IWICBitmapScaler; //图像比例变换接口
  begin
    WicImg := TWICImage.Create;
    Bitmap := TBitmap.Create;
    Jpg := TJPEGImage.Create;
    try
      Jpg.Assign(AGraphic);
      Jpg.CompressionQuality := 100;
      Jpg.Compress;
      Jpg.SaveToFile(TAppDir.GetAppTempDir + 'temp.jpg');
      WicImg.LoadFromFile(TAppDir.GetAppTempDir + 'temp.jpg');
      Factory := TWICImage.ImagingFactory;
      Factory.CreateBitmapScaler(Scaler);
      Scaler.Initialize(WicImg.Handle,  AWidth, AHeight,  WICBitmapInterpolationModeFant);
      WicImg.Handle := IWICBitmap(Scaler);      //ufUploadFile.UploadFile(WicImg, AFileName, UploadType);
      //WicImg.SaveToFile('C:\s2-wic500.jpg');
    finally
      Scaler := nil;
      Factory := nil;
      WicImg.Free;
      Jpg.Free;
      Bitmap.Free;
    end;
  end;

Answer 6

StretchDraw
改成
CopyRect可能多用个临时bitmap，不要用StretchDraw