image processing - Advise filters to improve text visibility on photo -


i need filters improve text visibility on photo, since has noise. filters (algorithms) know purpose?

now, use monochrome filter doesn't improve image quality. need filter can determine medium background of little area , make image monochrome depending on medium background.

for example picture background white , grey characters areas has darker color (grey) , black characters. need algorithm can understand area of image more darker , make level of black accepting lower.


for example, source image: photo
and processed photo (median, monochrome filters) processed photo

unfortunately i'm not able provide accurate , fast answer using image processing package in code, can provide hints based on quick tests done in photoshop(sorry, visual thinker, slow typist). worst case scenario, can run photoshop filters matlab, filters used should available or not difficult implement since i've constraint myself to:

  • curves
  • levels
  • high pass

in simple terms, recommend first getting read of gradient dark bright gradient: easier play contrast/threshold on more image. in photoshop applied curves (which other people wondered implementing in code)

curves curves settings

not perfect, illustrates idea of cancelling out bit of strong gradient.

on resulting image applied levels:

levels levels settings

afterwards, high pass:

high pass

you can use high pass result , blend (overlay) previous step emphasize details:

high pass + overlay

then apply stamp filter (a mixture of small gaussian blur + threshold):

stamp filter

or simpler, on high pass result, apply curves again or threshold:

curves curves settings

the idea threshold should deal segmentation @ last stage , need make it's job easy possible cancelling out elements not pertaining text (like flash light gradient). if need cleanup small dots later, morphological filter (like erode, dilate) should help. can find info on detecting gradients well.


Comments

Post a Comment

Popular posts from this blog

java - pagination of xlsx file to XSSFworkbook using apache POI -

right in code, reading xlsx file, xssfworkbook, , writing database. but, when size of xlsx file increases, causes outofmemory error. can not increase server size, or divide xlsx file pieces. tried loading workbook using file (instead of inputstream), didn't either. i looking way read 10k rows @ time (instead of entire file @ once) , iteratively write workbook , database. is there way apache poi? poi contains called "eventmodel" designed purpose. it's mentioned in faq : the ss eventmodel package api reading excel files without loading whole spreadsheet memory. require more knowledge on part of user, reduces memory consumption more tenfold. based on awt event model in combination sax. if need read-only access, best way it. however, may want double check first if issue somewhere else. check out this item : i think poi using memory! can do? 1 comes quite lot, reason isn't might think. so, first thing check - what's source of prob...
Read more

Unlimited choices in BASH case statement -

consider simple bash snippet: case $option in 1) image=${options[0]%.tar} ;; 2) image=${options[1]%.tar} ;; 3) image=${options[2]%.tar} ;; 4) image=${options[3]%.tar} ;; *) echo "invalid option" exit 1 esac in real script numbers goes 30. makes pretty long. can somehow specify cases variable? something this: case $option in $i) image=${options[$(($i-1))]%.tar} any pointer appreciated. you can match against multiple patterns in single clause: case $option in 1|2|3: echo "$option one, 2 or three" ;; esac if still typing you, can use simple pattern matching: case $option in # following matches # - single-digit numbers 0-9 # - two-digit numbers starting either 1 or 2 # - number 30 [0-9]|[12][0-9]|30) image=${options[$(($option-1))]%.tar} ;; *) echo "invalid option" 1>&2 exit 1 esac
Read more

apache - How do I stop my index.php being run twice for every user -

we've got webapp initial html served using apache , php. i noticed index.php being run twice every request. seems caused / effected rewrite rules in our .htaccess - rewritecond %{http_host} ^(www\.|hotels\.)ourdomain\.com$ [nc,or] rewritecond %{server_name} ^(www\.|hotels\.)ourdomain\.com$ [nc] rewriterule (.*) http://ourdomain.com/$1 [r=301] rewriterule ^hotels/([^/]+)/?\??(.*)$ ?d=$1&$2 [qsa] the final rule moving parameter url path query string. i.e. http://ourdomain.com/hotels/vegas?someparam=1 becomes http://ourdomain.com?d=vegas&someparam=1 if go directly query string version index.php run once. if use url redirected, index.php run twice (i'm checking adding error_log('end of index.php') file). so example going http://ourdomain.com/hotels/paris hits file twice http://ourdomain.com?d=paris hits once. i've seen this question , had @ blog mentioned , , can't find empty string url's (i've tried using yslow process). ...
Read more