diff --git a/autoload/colorizer.vim b/autoload/colorizer.vim
index 4d181ca..1a2d820 100644
--- a/autoload/colorizer.vim
+++ b/autoload/colorizer.vim
@@ -154,9 +154,9 @@ endfunction
 function! s:RgbaColor(str, lineno) "{{{2
   if has("gui_running")
     let bg = synIDattr(synIDtrans(hlID("Normal")), "bg")
-    let bg_r = str2nr(bg[1].bg[2], 16)
-    let bg_g = str2nr(bg[3].bg[4], 16)
-    let bg_b = str2nr(bg[5].bg[6], 16)
+    let bg_r = str2nr(bg[1:2], 16)
+    let bg_g = str2nr(bg[3:4], 16)
+    let bg_b = str2nr(bg[5:6], 16)
   else
     " translucent colors would display incorrectly, so ignore the alpha value
     return s:RgbaColorForTerm(a:str, a:lineno)
@@ -195,15 +195,9 @@ function! s:RgbaColor(str, lineno) "{{{2
     let r = float2nr(ceil(ar * alpha) + ceil(bg_r * (1 - alpha)))
     let g = float2nr(ceil(ag * alpha) + ceil(bg_g * (1 - alpha)))
     let b = float2nr(ceil(ab * alpha) + ceil(bg_b * (1 - alpha)))
-    if r > 255
-      let r = 255
-    endif
-    if g > 255
-      let g = 255
-    endif
-    if b > 255
-      let b = 255
-    endif
+    let r = min([r, 255])
+    let g = min([g, 255])
+    let b = min([b, 255])
     let l:color = printf('#%02x%02x%02x', r, g, b)
     call add(ret, [l:color, pat])
   endwhile
@@ -286,9 +280,22 @@ function! colorizer#ColorHighlight(update, ...) "{{{1
   if g:colorizer_fgcontrast != s:saved_fgcontrast || (exists("a:1") && a:1 == '!')
     let s:force_group_update = 1
   endif
-  for i in range(1, line("$"))
-    call s:PreviewColorInLine(i)
-  endfor
+
+  let cur_line = line("w0")
+  let end_line = line("w$")
+  while cur_line <= end_line
+    " skip folded lines
+    if foldclosed(cur_line) > 0
+      let cur_line = foldclosedend(cur_line) + 1
+    endif
+    call s:PreviewColorInLine(cur_line)
+    let cur_line += 1
+  endwhile
+
+  " A hack for colorizing after opening a folding
+  if ( winheight('.') - line('w$') + line('w0') ) > 1
+    autocmd CursorHold * silent call colorizer#ColorHighlight(1)
+  endif
   let s:force_group_update = 0
   let s:saved_fgcontrast = g:colorizer_fgcontrast
   augroup Colorizer
@@ -305,7 +312,8 @@ function! colorizer#ColorHighlight(update, ...) "{{{1
       autocmd CursorMoved,CursorMovedI * silent call s:CursorMoved()
     endif
     " rgba handles differently, so need updating
-    autocmd GUIEnter * silent call colorizer#ColorHighlight(1)
+    autocmd CursorMoved * silent call colorizer#ColorHighlight(1)
+    autocmd CursorMovedI * silent call colorizer#ColorHighlight(1)
     autocmd BufEnter * silent call colorizer#ColorHighlight(1)
     autocmd WinEnter * silent call colorizer#ColorHighlight(1)
     autocmd ColorScheme * let s:force_group_update=1 | silent call colorizer#ColorHighlight(1)