Finder

Be aware: Since 1.1.0 the behavior is changed compared to previous versions, to be consistent with Region.find()/findAll().

A Finder object implements an iterator of matches and allows to search for a visual object in an image file that you provide (e.g. a screenshot taken and saved in a file before). After setting up the finder object and doing a find operation, you can iterate through the found matches if any.

Be aware: an iterator can be stepped through only once - it is empty afterwards

Compared with the region based find/findAll operation, no exception FindFailed is raised in case nothing is found at all. Use hasNext() to check.

Note: There is no chance, to get the number of matches in advance. If you iterate through to count, afterwards your finder is empty. So you have to save your matches somehow while counting, if you need them later (one possible solution see example below).

The workflow always is (except for findChanges):

• setup a Finder
  • do a find or findAll operation
  • check with hasNext(), wether anything was found at all
  • get the available matches with next() if hasNext() says more are available
  • After a complete iteration, the finder object is empty.

You can start a new find or findAll operation on the same Finder object at any time.

Finder(path-to-imagefile)

Create a new finder object.

• path-to-imagefile — filename to a source image to search within

find(path-to-imagefile, [similarity])

Find a given image within a source image previously specified in the constructor of the finder object. If more than one match is possible, yet only one is returned and which one is not predictible.

• path-to-imagefile — the target image to search for
• similarity — the minimum similarity a match should have. If omitted, the default is used.

findAll(path-to-imagefile, [similarity])

Find all occurences of the given image within a source image previously specified in the constructor of the finder object.

• path-to-imagefile — the target image to search for
• similarity — the minimum similarity a match should have. If omitted, the default is used.

hasNext()

Check whether there are more matches available that satisfy the minimum similarity requirement. A False returned after the first hasNext() signals, that nothing was found at all.

Returns: True if more matches exist.

next()

Get the next match.

Returns: a Match object or None, if empty or no more matches.

The returned reference to a match object is no longer available in the finder object afterwards. So if it is needed later, it has to be saved to another variable.

findChanges(path-to-imagefile)

Find rectangle areas in an image (the one the Finder was created with), that differ from another image. This feature is the image variant of onChange in the Region observe feature for one-time-use.

• path-to-imagefile — the target image to compare with (exactly same size in pixels)

Returns: a list of Region objects (empty, if no changes where detected).

Note

Some Information on implementation

• both images are converted to grayscale
• only pixels whose gray value differs +-3 (PIXEL_DIFF) are looked at
• if more than 5 pixels are detected (IMAGE_DIFF) a change is assumed

You can set these values as needed after having created the Finder

• use finder.setFindChangesImageDiff(int value) to adjust PIXEL_DIFF
• use finder.setFindChangesImageDiff(int value) to adjust IMAGE_DIFF

With a new Finder object, the values are reset to the default

• use finder.resetFindChanges() to do this on the fly for a Finder object

Example 1: findAll using a Finder

create a Finder with your saved screenshot

f = Finder(“stars.png”) img= “star.png” # the image you are searching

f.findAll(img) # find all matches

while f.hasNext(): # loop as long there is a first and more matches print “found: ”, f.next() # access the next match in the row

print f.hasNext() # is False, because f is empty now

Example 2: we want to know how many matches in advance and want to save the matches for later use (based on the previous example).

create a Finder with your saved screenshot

f = Finder(“stars.png”) img= “star.png” # the image you are searching

f.findAll(img) # find all matches matches = [] # an empty list to store the matches

while f.hasNext(): # loop as long there is a first and more matches matches.append(f.next()) # access next match and add to matches

print f.hasNext() # is False, because f is empty now

now we have our matches saved in the list matches

print len(matches) # the number of matches

we want to use our matches

for m in matches: print m