This pull requests aims to provide convenient way to zoom in comics. The idea is when user holds/double taps (not decided yet) on a manga/comic panel, it gets cut out from the rest of the image and zoomed. More details in koreader/koreader-base#1148. Depends on koreader/koreader-base#1159
* Allow for colored rendering
Available with all engines (CRE, PDF, Images).
Needs to manually add setting: "color_rendering" = true
* Disable color for djvudocument
* Use Screen:isColorEnabled()
* Bump base
this should implement feature request of zoom mode for multi-columns
page in #501
This PR depends on koreader/koreader-base#435
How to use?
1. Tap the top left corner of a PDF/Djvu page to get into the flipping
mode
2. Double-tap on text block will zoom in to that column
3. Double-tap on any area will zoom out to an overview of the page
4. repeat step 2 to focus to another page block
How does it work?
1. We first find the mask of text blocks in the page. (Pic 1)
2. Then we intersect page boxes with user tap to form a page block. (Pic 2)
3. Finally we zoom the page to the page block and center current view to
that block. (Pic 3)
In regional zoom mode double tap will zoom to the tapped
region(paragraph or column, etc., detected optically via libk2pdfopt).
As the first demo, this feature is only turned on in flipping mode by
tapping the top-left corner of the screen. Eventually we may incorporate
this feature in "free" zoom mode.
and there is no need to OCR word if we can extract text from
original page in reflowing mode thanks to the rect maps between
normal page and reflowed page.