au.com.southsky.jfreesane

Interface ScanListener

All Known Implementing Classes:

ScanListenerAdapter

public interface ScanListener

Implementations of this interface can receive notifications when certain events happen during a page scan. To receive notifications, use the SaneDevice.acquireImage(ScanListener) method.

If you are only interested in a subset of these events, you may want to extend ScanListenerAdapter instead of implementing this interface.

If you are using ScanListener to update a user interface, the frequency of notifications (specifically from recordRead(au.com.southsky.jfreesane.SaneDevice, int, int)) may be too frequent. In this case, you can wrap your listener using one of the methods in RateLimitingScanListeners to obtain a listener that drops notifications occurring too frequently.

Notifications will tend to occur as follows:

1. scanningStarted -- once a page scan has commenced
2. frameAcquisitionStarted -- once for each frame. Typically there is only one frame per page, but in older three-pass color scanners (where one scan pass is made per color), there will be three frames per page
3. recordRead -- once for each record, one or more records make up a frame
4. scanningFinished -- once a page has been scanned

JFreeSane attempts to report accurate numbers to listeners, but this is not possible in all cases. In general, you should not depend on data obtained from the listener when this could affect program correctness.

Method Summary

Modifier and Type	Method and Description
void	frameAcquisitionStarted(SaneDevice device, au.com.southsky.jfreesane.SaneParameters parameters, int currentFrame, int likelyTotalFrames) Called once frame acquisition has begun.
void	recordRead(SaneDevice device, int totalBytesRead, int imageSizeBytes) Called once for each record in a frame.
void	scanningFinished(SaneDevice device) Called once the current page is done.
void	scanningStarted(SaneDevice device) Called once scanning has begun.

Method Detail

scanningStarted

void scanningStarted(SaneDevice device)

Called once scanning has begun.

Parameters:

device - the device that is now acquiring an image

frameAcquisitionStarted

void frameAcquisitionStarted(SaneDevice device,
                             au.com.southsky.jfreesane.SaneParameters parameters,
                             int currentFrame,
                             int likelyTotalFrames)

Called once frame acquisition has begun. Typically there is one frame per page, but in older three-pass color scanners (where one scan pass is made for each color) this method will be called three times during a successful scan.

Parameters:

device - the device that is acquiring the frame

parameters - the parameters of the acquisition

currentFrame - the zero-based index of the frame in the current scan (normally 0, but will be 0, 1 and 2 in successive calls for three-pass scanners)

likelyTotalFrames - the number of frames that are likely to be received in this scan. JFreeSane cannot know this for sure, so the number should not be relied upon for program correctness

recordRead

void recordRead(SaneDevice device,
                int totalBytesRead,
                int imageSizeBytes)

Called once for each record in a frame. A frame may consist of many records.

Parameters:

device - the device that acquired the record

totalBytesRead - the number of bytes read so far in this frame

imageSizeBytes - the total number of bytes in the frame. When this cannot be known in advance, this will be set to -1 (e.g. the scanner is a hand-held scanner or uses page height detection)

scanningFinished

void scanningFinished(SaneDevice device)

Called once the current page is done.

Parameters:

device - the device that is now finished acquiring a page