koreader/frontend/document/koptinterface.lua

require "dbg"
require "cache"
require "ui/geometry"
require "ui/device"
require "ui/reader/readerconfig"

KoptInterface = {
	tessocr_data = "data",
	ocr_lang = "eng",
	ocr_type = 0, -- default, for more accuracy use 3
}

ContextCacheItem = CacheItem:new{}

function ContextCacheItem:onFree()
	if self.kctx.free then
		DEBUG("free koptcontext", self.kctx)
		self.kctx:free()
	end
end

function KoptInterface:waitForContext(kc)
	-- if koptcontext is being processed in background thread
	-- the isPreCache will return 1.
	while kc and kc:isPreCache() == 1 do
		DEBUG("waiting for background rendering")
		util.usleep(100000)
	end
	return kc
end

--[[
get reflow context
--]]
function KoptInterface:createContext(doc, pageno, bbox)
	-- Now koptcontext keeps track of its dst bitmap reflowed by libk2pdfopt.
	-- So there is no need to check background context when creating new context.
	local kc = KOPTContext.new()
	local screen_size = Screen:getSize()
	kc:setTrim(doc.configurable.trim_page)
	kc:setWrap(doc.configurable.text_wrap)
	kc:setIndent(doc.configurable.detect_indent)
	kc:setRotate(doc.configurable.screen_rotation)
	kc:setColumns(doc.configurable.max_columns)
	kc:setDeviceDim(screen_size.w, screen_size.h)
	kc:setDeviceDPI(doc.screen_dpi)
	kc:setStraighten(doc.configurable.auto_straighten)
	kc:setJustification(doc.configurable.justification)
	kc:setZoom(doc.configurable.font_size)
	kc:setMargin(doc.configurable.page_margin)
	kc:setQuality(doc.configurable.quality)
	kc:setContrast(doc.configurable.contrast)
	kc:setDefectSize(doc.configurable.defect_size)
	kc:setLineSpacing(doc.configurable.line_spacing)
	kc:setWordSpacing(doc.configurable.word_spacing)
	kc:setBBox(bbox.x0, bbox.y0, bbox.x1, bbox.y1)
	if Dbg.is_on then kc:setDebug() end
	return kc
end

function KoptInterface:getContextHash(doc, pageno, bbox)
	local screen_size = Screen:getSize()
	local screen_size_hash = screen_size.w.."|"..screen_size.h
	local bbox_hash = bbox.x0.."|"..bbox.y0.."|"..bbox.x1.."|"..bbox.y1
	return doc.file.."|"..pageno.."|"..doc.configurable:hash("|").."|"..bbox_hash.."|"..screen_size_hash
end

function KoptInterface:getAutoBBox(doc, pageno)
	local bbox = {
		x0 = 0, y0 = 0,
		x1 = 0, y1 = 0,
	}
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local hash = "autobbox|"..context_hash
	local cached = Cache:check(hash)
	if not cached then
		local page = doc._document:openPage(pageno)
		local kc = self:createContext(doc, pageno, bbox)
		bbox.x0, bbox.y0, bbox.x1, bbox.y1 = page:getAutoBBox(kc)
		DEBUG("Auto detected bbox", bbox)
		page:close()
		Cache:insert(hash, CacheItem:new{ autobbox = bbox })
		return bbox
	else
		return cached.autobbox
	end
end

function KoptInterface:getPageText(doc, pageno)
	local bbox = doc:getPageBBox(pageno)
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local hash = "pgtext|"..context_hash
	local cached = Cache:check(hash)
	if not cached then
		local kctx_hash = "kctx|"..context_hash
		local cached = Cache:check(kctx_hash)
		if cached then
			local kc = self:waitForContext(cached.kctx)
			local fullwidth, fullheight = kc:getPageDim()
			local text = kc:getWordBoxes(0, 0, fullwidth, fullheight)
			Cache:insert(hash, CacheItem:new{ pgtext = text })
			return text
		end
	else
		return cached.pgtext
	end
end

function KoptInterface:getOCRWord(doc, pageno, rect)
	local bbox = doc:getPageBBox(pageno)
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local hash = "ocrword|"..context_hash..rect.x..rect.y..rect.w..rect.h
	local cached = Cache:check(hash)
	if not cached then
		local kctx_hash = "kctx|"..context_hash
		local cached = Cache:check(kctx_hash)
		if cached then
			local kc = self:waitForContext(cached.kctx)
			local fullwidth, fullheight = kc:getPageDim()
			local ok, word = pcall(
				kc.getOCRWord, kc,
				self.tessocr_data,
				self.ocr_lang,
				self.ocr_type, 
				rect.x, rect.y,
				rect.w, rect.h)
			Cache:insert(hash, CacheItem:new{ ocrword = word })
			return word
		end
	else
		return cached.ocrword
	end
end

--[[
get cached koptcontext for centain page. if context doesn't exist in cache make
new context and reflow the src page immediatly, or wait background thread for 
reflowed context.
--]]
function KoptInterface:getCachedContext(doc, pageno)
	local bbox = doc:getPageBBox(pageno)
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local kctx_hash = "kctx|"..context_hash
	local cached = Cache:check(kctx_hash)
	if not cached then
		-- If kctx is not cached, create one and get reflowed bmp in foreground.
		local kc = self:createContext(doc, pageno, bbox)
		local page = doc._document:openPage(pageno)
		-- reflow page
		--local secs, usecs = util.gettime()
		page:reflow(kc, 0)
		page:close()
		--local nsecs, nusecs = util.gettime()
		--local dur = nsecs - secs + (nusecs - usecs) / 1000000
		--DEBUG("Reflow duration:", dur)
		--self:logReflowDuration(pageno, dur)
		local fullwidth, fullheight = kc:getPageDim()
		DEBUG("reflowed page", pageno, "fullwidth:", fullwidth, "fullheight:", fullheight)
		Cache:insert(kctx_hash, ContextCacheItem:new{ kctx = kc })
		return kc
	else
		-- wait for background thread
		return self:waitForContext(cached.kctx)
	end
end

--[[
get reflowed page dimensions
--]]
function KoptInterface:getPageDimensions(doc, pageno, zoom, rotation)
	local kc = self:getCachedContext(doc, pageno)
	local fullwidth, fullheight = kc:getPageDim()
	return Geom:new{ w = fullwidth, h = fullheight }
end

--[[
inherited from common document interface
render reflowed page into tile cache.
--]] 
function KoptInterface:renderPage(doc, pageno, rect, zoom, rotation, render_mode)
	doc.render_mode = render_mode
	local bbox = doc:getPageBBox(pageno)
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local renderpg_hash = "renderpg|"..context_hash

	local cached = Cache:check(renderpg_hash)
	if not cached then
		-- do the real reflowing if kctx is not been cached yet
		local kc = self:getCachedContext(doc, pageno)
		local fullwidth, fullheight = kc:getPageDim()
		if not Cache:willAccept(fullwidth * fullheight / 2) then
			-- whole page won't fit into cache
			error("aborting, since we don't have enough cache for this page")
		end
		local page = doc._document:openPage(pageno)
		-- prepare cache item with contained blitbuffer
		local tile = CacheItem:new{
			size = fullwidth * fullheight / 2 + 64, -- estimation
			excerpt = Geom:new{ w = fullwidth, h = fullheight },
			pageno = pageno,
			bb = Blitbuffer.new(fullwidth, fullheight)
		}
		page:rfdraw(kc, tile.bb)
		page:close()
		Cache:insert(renderpg_hash, tile)
		return tile
	else
		return cached
	end
end

--[[
inherited from common document interface
render reflowed page into cache in background thread. this method returns immediatly
leaving the precache flag on in context. subsequent usage of this context should 
wait for the precache flag off by calling self:waitForContext(kctx)
--]]
function KoptInterface:hintPage(doc, pageno, zoom, rotation, gamma, render_mode)
	local bbox = doc:getPageBBox(pageno)
	local context_hash = self:getContextHash(doc, pageno, bbox)
	local kctx_hash = "kctx|"..context_hash
	local cached = Cache:check(kctx_hash)
	if not cached then
		local kc = self:createContext(doc, pageno, bbox)
		local page = doc._document:openPage(pageno)
		DEBUG("hinting page", pageno, "in background")
		-- reflow will return immediately and running in background thread
		kc:setPreCache()
		page:reflow(kc, 0)
		page:close()
		Cache:insert(kctx_hash, ContextCacheItem:new{ kctx = kc })
	end
end

--[[
inherited from common document interface
draw cached tile pixels into target blitbuffer.
--]]
function KoptInterface:drawPage(doc, target, x, y, rect, pageno, zoom, rotation, render_mode)
	local tile = self:renderPage(doc, pageno, rect, zoom, rotation, render_mode)
	--DEBUG("now painting", tile, rect)
	target:blitFrom(tile.bb,
		x, y,
		rect.x - tile.excerpt.x,
		rect.y - tile.excerpt.y,
		rect.w, rect.h)
end

--[[
helper functions
--]]
function KoptInterface:logReflowDuration(pageno, dur)
	local file = io.open("reflowlog.txt", "a+")
	if file then
		if file:seek("end") == 0 then -- write the header only once
			file:write("PAGE\tDUR\n")
		end
		file:write(string.format("%s\t%s\n", pageno, dur))
		file:close()
	end
end