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Date Posted: 10:03:50 06/06/01 Wed
Author: Ann Weaver
Subject: Speed Issue in conversion from B/W to Grayscale
In reply to: Michel 's message, "Re: How save BW image as JPEG?" on 17:47:42 06/04/01 Mon


Good Morning Michel,

Well, in further testing last night I have determined that it is definitely the conversion that is time consuming. It consistently takes 10 seconds on every scan. If I remark out the conversion code it is ready to save the image almost immediately (and will if changed to a .tif format instead of .jpg). If I leave the conversion code in and remark out the resize coding, the speed is again back to 10 seconds. Maybe there is something wrong with the way I am doing the conversion???

I have included a sample of my coding below. I am using the Pegasus Tools TwainPRO and SmartScan Xpress Barcode packages as well to capture the image from the scanner and read the barcode. I am then using the Envision components to convert the image and elsewhere in the application to zoom, etc.

I am performing the following on the PostScan event of the TwainPRO object.

procedure TdmData.TwnPROPostScan(Sender: TObject; Cancel: WordBool);
var
BarcodeNbr, DocumentName: String;
DocumentNbr: Integer;
ImageScrollBox: TImageScrollBox;
FormatTransform: TImageFormatTransform;
ResizeTransform: TResizeTransform;
begin
Screen.Cursor := crHourglass;

{ Copy scanned image to the clipboard & read the barcode }

{ Setup the filename based on the barcode detected }

{ Create a temp image }
ImageScrollBox := TImageScrollBox.Create(Self);
ImageScrollBox.Graphic.AssignFromDIBHandle(TwnPRO.hDib);

{ Change to Grayscale image so it can be saved as a JPEG }
FormatTransform := TImageFormatTransform.Create;
try
FormatTransform.ImageFormat := ifGray256;
FormatTransform.Apply(ImageScrollBox.Graphic);
finally
FormatTransform.Free;
end;

{ Resize Image by 50% }
ResizeTransform := TResizeTransform.Create;
try
ResizeTransform.Width := StrToInt(FloatToStr(Int(StrToFloat(IntToStr(ImageScrollBox.Graphic.Width)) * 0.5)));
ResizeTransform.Height := StrToInt(FloatToStr(Int(StrToFloat(IntToStr(ImageScrollBox.Graphic.Height)) * 0.5)));
ResizeTransform.Apply(ImageScrollBox.Graphic);
finally
ResizeTransform.Free;
end;

{ Save the image }
try
ImageScrollBox.SaveToFile(ADOtblOptionsImagePath.AsString + DocumentName);
except
{ handle exceptions }
end;

{ Release resources }
ImageScrollBox.Free;

{ Add index to database }
try
with ADOtblImgIndex do
begin
Insert;
ADOtblImgIndexFileName.AsString := DocumentName;
ADOtblImgIndexScanDate.AsDateTime := Now;
Post;
end;
except
{ handle exceptions }
end;

Inc(ImageCount);
Screen.Cursor := crDefault;
end;


>
>Hi Ann,
>
>I would assume the resize is the more time consuming.
>The conversion should be fast even on large images.
>For the resizing, are you using interpolation on the
>TResizeTransform. I would try it without
>interpolation, and the quality may still be very
>acceptable.
>
>Best regards,
>
>Michel
>
>
>>
>>I have this all working now but is running fairly slow
>>due to the conversion from B/W to Grayscale. I am
>>scanning the images at B/W 300dpi which seems to be
>>about the minimum I can go and still get a good read
>>of the barcode contained in the image. However, due
>>to the size of the image it makes the conversion from
>>B/W to grayscale take about 10 seconds or so to
>>convert (which is a necessity to store the image as
>>.jpg). I then resize the image as I don't need/want to
>>store an image of that size. If I resize the image
>>prior to the conversion it goes faster but I lost a
>>lot of image quality that way. Conversion first, then
>>resize works great but lacking speed.
>>
>>Does anyone have any suggestions on how to speed up
>>this process?
>>
>>Thanks!
>>Ann
>>

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