diff --git a/frontend/document/document.lua b/frontend/document/document.lua
index 2dee7dfde..bcd280a9d 100644
--- a/frontend/document/document.lua
+++ b/frontend/document/document.lua
@@ -220,4 +220,5 @@ end
 
 require "document/pdfdocument"
 require "document/djvudocument"
+require "document/koptdocument"
 require "document/credocument"
diff --git a/frontend/document/koptdocument.lua b/frontend/document/koptdocument.lua
new file mode 100644
index 000000000..11be1c0b2
--- /dev/null
+++ b/frontend/document/koptdocument.lua
@@ -0,0 +1,197 @@
+require "cache"
+require "ui/geometry"
+require "ui/screen"
+require "ui/device"
+
+-- Any document processed by K2pdfopt is called a koptdocument
+KoptDocument = Document:new{
+	_document = false,
+	-- muPDF manages its own additional cache
+	mupdf_cache_size = 5 * 1024 * 1024,
+	djvulibre_cache_size = nil,
+	dc_null = DrawContext.new(),
+	screen_size = Screen:getSize(),
+	screen_dpi = Device:getModel() == "KindlePaperWhite" and 212 or 167,
+	configurable = {
+		font_size = 1.2,
+		page_margin = 0.06,
+		line_spacing = 1.2,
+		word_spacing = 0.15,
+		quality = 1.0,
+		text_wrap = 1,
+		defect_size = 1.0,
+		trim_page = 1,
+		detect_indent = 1,
+		multi_threads = 0,
+		auto_straighten = 0,
+		justification = -1,
+		max_columns = 2,
+		contrast = 1.0,
+		screen_rotation = 0,
+	}
+}
+
+function KoptDocument:init()
+	self.file_type = string.lower(string.match(self.file, ".+%.([^.]+)") or "")
+	if self.file_type == "pdf" then
+		local ok
+		ok, self._document = pcall(pdf.openDocument, self.file, self.mupdf_cache_size)
+		if not ok then
+			self.error_message = self.doc -- will contain error message
+			return
+		end
+		self.is_open = true
+		self.info.has_pages = true
+		if self._document:needsPassword() then
+			self.is_locked = true
+		else
+			self:_readMetadata()
+		end
+		
+	elseif self.file_type == "djvu" then
+		if not validDjvuFile(self.file) then
+			self.error_message = "Not a valid DjVu file"
+			return
+		end
+	
+		local ok
+		ok, self._document = pcall(djvu.openDocument, self.file, self.djvulibre_cache_size)
+		if not ok then
+			self.error_message = self.doc -- will contain error message
+			return
+		end
+		self.is_open = true
+		self.info.has_pages = true
+		self:_readMetadata()
+	end
+end
+
+function KoptDocument:unlock(password)
+	if not self._document:authenticatePassword(password) then
+		self._document:close()
+		return false, "wrong password"
+	end
+	self.is_locked = false
+	return self:_readMetadata()
+end
+
+-- check DjVu magic string to validate
+function validDjvuFile(filename)
+	f = io.open(filename, "r")
+	if not f then return false end
+	local magic = f:read(8)
+	f:close()
+	if not magic or magic ~= "AT&TFORM" then return false end
+	return true
+end
+
+function KoptDocument:getUsedBBox(pageno)
+	if self.file_type == "pdf" then
+		local hash = "pgubbox|"..self.file.."|"..pageno
+		local cached = Cache:check(hash)
+		if cached then
+			return cached.data
+		end
+		local page = self._document:openPage(pageno)
+		local used = {}
+		local native_dim = self:getNativePageDimensions(pageno)
+		used.x, used.y, used.w, used.h = 0, 0, native_dim.w, native_dim.h
+		Cache:insert(hash, CacheItem:new{ used })
+		page:close()
+		return used
+	elseif self.file_type == "djvu" then
+		-- djvu does not support usedbbox, so fake it.
+		local used = {}
+		local native_dim = self:getNativePageDimensions(pageno)
+		used.x, used.y, used.w, used.h = 0, 0, native_dim.w, native_dim.h
+		return used
+	end
+end
+
+-- get reflow context
+function KoptDocument:getKOPTContext(pageno)
+	local kc = KOPTContext.new()
+	kc:setTrim(self.configurable.trim_page)
+	kc:setWrap(self.configurable.text_wrap)
+	kc:setIndent(self.configurable.detect_indent)
+	kc:setRotate(self.configurable.screen_rotation)
+	kc:setColumns(self.configurable.max_columns)
+	kc:setDeviceDim(self.screen_size.w, self.screen_size.h)
+	kc:setDeviceDPI(self.screen_dpi)
+	kc:setStraighten(self.configurable.auto_straighten)
+	kc:setJustification(self.configurable.justification)
+	kc:setZoom(self.configurable.font_size)
+	kc:setMargin(self.configurable.page_margin)
+	kc:setQuality(self.configurable.quality)
+	kc:setContrast(self.configurable.contrast)
+	kc:setDefectSize(self.configurable.defect_size)
+	kc:setLineSpacing(self.configurable.line_spacing)
+	kc:setWordSpacing(self.configurable.word_spacing)
+	local bbox = self:getUsedBBox(pageno)
+	kc:setBBox(bbox.x, bbox.y, bbox.w, bbox.h)
+	return kc
+end
+
+-- calculates page dimensions
+function KoptDocument:getPageDimensions(pageno, zoom, rotation)
+	-- check cached page size
+	local hash = "pgrfsize|"..self.file.."|"..pageno
+	local cached = Cache:check(hash)
+	if not cached then
+		DEBUG("Warnning: cannot determine page size before reflowing.")
+		return Screen:getSize()
+	end
+	DEBUG("Found cached page size on page", pageno, cached[1])
+	return cached[1]
+end
+
+function KoptDocument:renderPage(pageno, rect, zoom, rotation, render_mode)
+	local hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation
+	--local page_size = self:getPageDimensions(pageno, zoom, rotation)
+	local kc = self:getKOPTContext(pageno)
+	local page = self._document:openPage(pageno)
+	-- reflow page
+	page:reflow(kc, render_mode)
+	local fullwidth, fullheight = kc:getPageDim()
+	DEBUG("page::reflowPage:", "fullwidth:", fullwidth, "fullheight:", fullheight)
+	local page_size = Geom:new{ w = fullwidth, h = fullheight }
+	-- cache reflowed page size
+	local pgrfsize_hash = "pgrfsize|"..self.file.."|"..pageno
+	if not Cache:check(pgrfsize_hash) then
+		Cache:insert(pgrfsize_hash, CacheItem:new{ page_size })
+	end
+	-- this will be the size we actually render
+	local size = page_size
+	-- we prefer to render the full page, if it fits into cache
+	if not Cache:willAccept(size.w * size.h / 2) then
+		-- whole page won't fit into cache
+		DEBUG("rendering only part of the page")
+		-- TODO: figure out how to better segment the page
+		if not rect then
+			DEBUG("aborting, since we do not have a specification for that part")
+			-- required part not given, so abort
+			return
+		end
+		-- only render required part
+		hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..tostring(rect)
+		size = rect
+	end
+
+	-- prepare cache item with contained blitbuffer	
+	local tile = CacheItem:new{
+		size = size.w * size.h / 2 + 64, -- estimation
+		excerpt = size,
+		pageno = pageno,
+		bb = Blitbuffer.new(size.w, size.h)
+	}
+
+	-- draw to blitbuffer
+	page:rfdraw(kc, tile.bb)
+	page:close()
+	Cache:insert(hash, tile)
+
+	return tile
+end
+
+DocumentRegistry:addProvider("pdf", "application/pdf", KoptDocument)
+DocumentRegistry:addProvider("djvu", "application/djvu", KoptDocument)
diff --git a/frontend/ui/reader/readerview.lua b/frontend/ui/reader/readerview.lua
index 6f9c1ce94..442210cf7 100644
--- a/frontend/ui/reader/readerview.lua
+++ b/frontend/ui/reader/readerview.lua
@@ -44,6 +44,7 @@ function ReaderView:paintTo(bb, x, y)
 			self.state.zoom,
 			self.state.rotation,
 			self.render_mode)
+		self:recalculate()
 	else
 		self.ui.document:drawCurrentView(
 			bb,
diff --git a/koptcontext.c b/koptcontext.c
index 0a810d310..329693b5f 100644
--- a/koptcontext.c
+++ b/koptcontext.c
@@ -26,6 +26,7 @@ static int newKOPTContext(lua_State *L) {
 	int columns = 2;
 	int offset_x = 0;
 	int offset_y = 0;
+	int dev_dpi = 167;
 	int dev_width = 600;
 	int dev_height = 800;
 	int page_width = 600;
@@ -58,6 +59,7 @@ static int newKOPTContext(lua_State *L) {
 	kc->columns = columns;
 	kc->offset_x = offset_x;
 	kc->offset_y = offset_y;
+	kc->dev_dpi = dev_dpi;
 	kc->dev_width = dev_width;
 	kc->dev_height = dev_height;
 	kc->page_width = page_width;
@@ -146,6 +148,12 @@ static int kcGetOffset(lua_State *L) {
 	return 2;
 }
 
+static int kcSetDeviceDPI(lua_State *L) {
+	KOPTContext *kc = (KOPTContext*) luaL_checkudata(L, 1, "koptcontext");
+	kc->dev_dpi = luaL_checkint(L, 2);
+	return 0;
+}
+
 static int kcSetDeviceDim(lua_State *L) {
 	KOPTContext *kc = (KOPTContext*) luaL_checkudata(L, 1, "koptcontext");
 	kc->dev_width = luaL_checkint(L, 2);
@@ -243,6 +251,7 @@ static const struct luaL_Reg koptcontext_meth[] = {
 	{"setOffset", kcSetOffset},
 	{"getOffset", kcGetOffset},
 	{"setDeviceDim", kcSetDeviceDim},
+	{"setDeviceDPI", kcSetDeviceDPI},
 	{"getPageDim", kcGetPageDim},
 	{"setStraighten", kcSetStraighten},
 	{"setJustification", kcSetJustification},
diff --git a/libk2pdfopt b/libk2pdfopt
index d9ed4f0b5..2e18531e4 160000
--- a/libk2pdfopt
+++ b/libk2pdfopt
@@ -1 +1 @@
-Subproject commit d9ed4f0b5d9212cdcc97fa432b83ba46eab21d09
+Subproject commit 2e18531e4d48f46eba8c12749723ba23417b8920