Images to grayscale

[madeinlisboa]

I'm sorry if this is a dup, but I searched and found nothing.

Is it possible to change images to grayscale when a book is converted? In this case from CHM to MOBI. It would lower substantially the final size.

[madeinlisboa]

Please, is my question senseless?

[kovidgoyal]

No, it isn't.

[madeinlisboa]

And?....

[DoctorOhh]

Originally Posted by kovidgoyal

No, it isn't.

I've grouped things above so you'll understand the answer.

[madeinlisboa]

First, I thought that mr. kovidgoyal was being ironic (his answer was right after my second question and it fitted perfectly), and now YOU are being ironic. What it the matter with you people in this forum?

[scissors]

Originally Posted by madeinlisboa

I'm sorry if this is a dup, but I searched and found nothing.

Is it possible to change images to grayscale when a book is converted? In this case from CHM to MOBI. It would lower substantially the final size.

Wouldn't this be useful for news recipes that grab lots of photos - which will only be displayed on B&W e-ink devices?

Could this command be added Kovid?

[Starson17]

Originally Posted by scissors

Wouldn't this be useful for news recipes that grab lots of photos - which will only be displayed on B&W e-ink devices?

I assume you are trying to save space?

Could this command be added Kovid?

I've used ImageMagick in recipes (calibre.utils.magick import Image) to rotate images. I'm not familiar with how much of ImageMagick is supported in Calibre, but there are sepia tone and grayscale separation commands in ImageMagick that might already be supported?

[scissors]

Originally Posted by Starson17

I assume you are trying to save space?

Exactly.

Originally Posted by Starson17

I've used ImageMagick in recipes (calibre.utils.magick import Image) to rotate images. I'm not familiar with how much of ImageMagick is supported in Calibre, but there are sepia tone and grayscale separation commands in ImageMagick that might already be supported?

I'm only a thick windows user. I've never head of imagemagik. I managed to figure out calibre.utils.magick import Image needs the FROM command to import it. The recipe accepted this.

I went to an imagemagik sit and found the -colorspace command. I tried colorspace=gray but calibre gives errors.

Other commands seem to need actual filenames in the command line?

I'm not sure how much calibre uses and even how to implement what it does use.

Can you give a link to your rotate example - is it somewhere in the re-usable code section?

[jackie_w]

Originally Posted by scissors

I went to an imagemagik sit and found the -colorspace command. I tried colorspace=gray but calibre gives errors.

Does colorspace='GRAYColorspace' work any better?

[Starson17]

Originally Posted by scissors

I went to an imagemagik sit and found the -colorspace command. I tried colorspace=gray but calibre gives errors.

Did you implement it in a recipe and import as needed? My code for rotating images is in the sticky code thread of the recipe forum. You can see there how I used the rotate options.

Spoiler:

#Add these imports
from calibre.utils.magick import Image, PixelWand

    def postprocess_html(self, soup, first):
        #process all the images. assumes that the new html has the correct path
        for tag in soup.findAll(lambda tag: tag.name.lower()=='img' and tag.has_key('src')):
            iurl = tag['src']
            img = Image()
            img.open(iurl)
            width, height = img.size
            print 'img is: ', iurl, 'width is: ', width, 'height is: ', height 
            if img < 0:
                raise RuntimeError('Out of memory')
            pw = PixelWand()
            if( width > height ) :
                print 'Rotate image'
                img.rotate(pw, -90)
                img.save(iurl)
        return soup

[scissors]

Thanks for the replies guys

both
colorspace='GRAYColorspace'
img.colorspace='GRAYColorspace'

compile. I added starson's code to the end of the Sun via google recipe.
Images rotate, but are still colour. :-(

I put the command in both IF statements to try and cover all bases, but nothing seems to happen.

Spoiler:

import urllib, re, mechanize
from calibre.web.feeds.recipes import BasicNewsRecipe
from calibre import __appname__
from calibre.utils.magick import Image, PixelWand

class GoogleReader(BasicNewsRecipe):
    title   = 'The Sun UK Via Google Reader2'
    
    #last updated 30/10/11 tidyied some stray classes

    cover_url = 'http://www.thesun.co.uk/img/global/new-masthead-logo.png'
     
    description = 'A Recipe for The Sun tabloid UK using the google reader recipe. You need to set up a gmail account solely for the reader, then subscribe to the suns RSS feeds at http://www.thesun.co.uk/sol/homepage...icle247949.ece'
    needs_subscription = True
    __author__ = ' Dave Asbury, davec, rollercoaster, Starson17'
    base_url = 'http://www.google.com/reader/atom/'
    oldest_article = 1
    max_articles_per_feed = 20
    get_options = '?n=%d&xt=user/-/state/com.google/read' % max_articles_per_feed
   # use_embedded_content = True

    masthead_url = 'http://www.thesun.co.uk/sol/img/global/Sun-logo.gif'
    #encoding = 'iso-8859-1'
    
    encoding = 'cp1252'
    remove_empty_feeds = True
    remove_javascript     = True
    no_stylesheets = True
    
    extra_css  = '''
	body{ text-align: justify; font-family:Arial,Helvetica,sans-serif; font-size:11px; font-size-adjust:none; font-stretch:normal; font-style:normal; font-variant:normal; font-weight:normal;}
                	 '''
    
    preprocess_regexps = [
    (re.compile(r'<div class="foot-copyright".*?</div>', re.IGNORECASE | re.DOTALL), lambda match: '')]
    
      
   
    keep_only_tags = [
                               dict(name='h1'),dict(name='h2',attrs={'class' : 'medium centered'}),
	           dict(name='div',attrs={'class' : 'text-center'}),
	           dict(name='div',attrs={'id' : 'bodyText'})
	           # dict(name='p')
	           ]
    remove_tags=[
	       #dict(name='head'),
	       dict(attrs={'class' : ['mystery-meat-link','ltbx-container','ltbx-var ltbx-hbxpn','ltbx-var ltbx-nav-loop','ltbx-var ltbx-url']}),
                           dict(name='div',attrs={'class' : 'cf'}),
	       dict(attrs={'title' : 'download flash'}),
                           dict(attrs={'style' : 'padding: 5px'})
	      
	       ]
    
   

    def get_browser(self):
        br = BasicNewsRecipe.get_browser(self)
        if self.username is not None and self.password is not None:
            request = urllib.urlencode([('Email', self.username), ('Passwd', self.password),
                                        ('service', 'reader'), ('accountType', 'HOSTED_OR_GOOGLE'), ('source', __appname__)])
            response = br.open('https://www.google.com/accounts/ClientLogin', request)
            auth = re.search('Auth=(\S*)', response.read()).group(1)
            cookies = mechanize.CookieJar()
            br = mechanize.build_opener(mechanize.HTTPCookieProcessor(cookies))
            br.addheaders = [('Authorization', 'GoogleLogin auth='+auth)]
        return br
    

    def get_feeds(self):
        feeds = []
        soup = self.index_to_soup('http://www.google.com/reader/api/0/tag/list')
        for id in soup.findAll(True, attrs={'name':['id']}):
            url = id.contents[0]
            feeds.append((re.search('/([^/]*)$', url).group(1),
                          self.base_url + urllib.quote(url.encode('utf-8')) + self.get_options))
        return feeds

    def postprocess_html(self, soup, first):
        #process all the images. assumes that the new html has the correct path
        for tag in soup.findAll(lambda tag: tag.name.lower()=='img' and tag.has_key('src')):
            iurl = tag['src']
            img = Image()
            img.open(iurl)
            width, height = img.size
            print 'img is: ', iurl, 'width is: ', width, 'height is: ', height 
            colorspace='GRAYColorspace'
            img.colorspace='GRAYColorspace'
            if img < 0:
                raise RuntimeError('Out of memory')
            pw = PixelWand()
            if( width > height ) :
                print 'Rotate image'
                colorspace='GRAYColorspace'
                img.rotate(pw, -90)
                img.colorspace='GRAYColorspace'
                img.save(iurl)
        return soup
        #auto_cleanup = True

[alansplace]

Originally Posted by madeinlisboa

I'm sorry if this is a dup, but I searched and found nothing.

Is it possible to change images to grayscale when a book is converted? In this case from CHM to MOBI. It would lower substantially the final size.

i'd try this workflow:

1. convert to epub using calibre
2. use calibre's right click option 'tweak epub' to explode the epub
3. use IrfanView (free software at cnet) to batch convert all the graphics files.
4. rebuild the epub using the tweak epub window (it should still be open).
5. convert the epub to mobi with calibre.

[jackie_w]

@scissors, I don't claim to know anything about News recipes but I've used the following command in my Calibre plugin to convert an image to greyscale

img.quantize(number_colors=8, colorspace='GRAYColorspace')

[Starson17]

Originally Posted by scissors

Thanks for the replies guys

both
colorspace='GRAYColorspace'
img.colorspace='GRAYColorspace'

compile. I added starson's code to the end of the Sun via google recipe.
Images rotate, but are still colour. :-(

That code won't do it. This will:

Spoiler:

    def postprocess_html(self, soup, first):
        #process all the images
        for tag in soup.findAll(lambda tag: tag.name.lower()=='img' and tag.has_key('src')):
            iurl = tag['src']
            img = Image()
            img.open(iurl)
            if img < 0:
                raise RuntimeError('Out of memory')
            img.type = "GrayscaleType"
            img.save(iurl)
        return soup

It saved 3KB from a 38KB image