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Date Posted: 09:06:12 06/12/01 Tue
Author: Ann Weaver
Subject: Re: Speed Issue in conversion from B/W to Grayscale
In reply to: Michel 's message, "Re: Speed Issue in conversion from B/W to Grayscale" on 06:49:08 06/08/01 Fri


Good Morning Michel,

Wow! That cut the conversion time by 50%! Now there is only a 5 second delay between scans. This is much more acceptable. Thanks so much for your help.

Ann


>
>Hi Ann,
>
>By default the ImageFormatTransform Dither and
>Quantize property are set True. Try turning both off,
>and each individual and compare the speed/quality.
>Since the origina is B/W, both False will probably be
>fine.
>
>ie,
>
>FormatTransform.Dither := False;
>FormatTransform.Quantize := False;
>
>Best regards,
>
>Michel
>
>>
>>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(ImageScrol
>l
>>Box.Graphic.Width)) * 0.5)));
>> ResizeTransform.Height :=
>>StrToInt(FloatToStr(Int(StrToFloat(IntToStr(ImageScrol
>l
>>Box.Graphic.Height)) * 0.5)));
>> ResizeTransform.Apply(ImageScrollBox.Graphic);
>> finally
>> ResizeTransform.Free;
>> end;
>>
>> { Save the image }
>> try
>>
>>ImageScrollBox.SaveToFile(ADOtblOptionsImagePath.AsStr
>i
>>ng + 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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