Re: Scan to Lossless Image

I'm using acquirefast with c# in version 19. How do I scan to a lossless jpeg. I do not see a way to set the CodecsJpegSaveOptions.QualityFactor to 0.

mesa,

If you want to use the Twain driver's own compression, I don't think you'll find a driver that supports lossless JPEG because it's not a common format.

However, our own image compression support lossless JPEG among countless other image types.
If you wish to save this format, you can use the Acquire() method and handle the AcquirePage event. From the event, you can set the quality factor of the JPEG image to 0 by using the following line:
_codecs.Options.Jpeg.Save.QualityFactor = 0;

Important notes:
1- The _codecs is a variable of type Leadtools.Codecs.RasterCodecs.
2- This format (Lossless JPEG) is not supported by some common viewers, so verify which viewer is going to be used to display it before you decide to use it.

So if I'm understanding right, the only way to control the different possible jpeg and png compression levels when saving a scanned image is to use Acquire, because these settings are not supported by AcquireFast.

This seems to be a significant oversight in the implementation of AcquireFast. Is there any way to submit this as a request.

Another question, what is the level of jpeg compression used when saving an image using AcquireFast? What is the level of png compression used when saving an image using AcquireFast?

mesa,

With AcquireFast (our Fast Twain features), the compression is actually performed by the Twain device's driver (data source), so the compression will depend on the scanner and not our toolkit. That's how fast Twain achieves maximum speed when you have a high-performance scanner.

About determining the level of compression, some scanners have a capability called ICAP_JPEGQUALITY. The capability can be used to get the level of compression and set it if it's supported by the scanner. For the PNG format, I'm afraid that I didn't find anything similar to JPEG. If the scanner supports more than one type of compression, use the ICAP_COMPRESSION capability which can be used to determine the type of required compression.

If your scanner does not support these capbalities, you can have control over the compression type and target format of the image using software (Acquire() method and codecs.Save() method). If you have a high-spec computer, you might even get speeds similar to Fast Twain because both our JPEG and PNG compressors are optimized.