image.scale: remove rational dependency and support "*SC" and "*SCn/SCd"scalefactor

3 files changed, 49 insertions, 28 deletions

diff --git a/doc/simpletransform.md b/doc/simpletransform.md
index 5b713c7..8c0cfb0 100644
--- a/doc/simpletransform.md
+++ b/doc/simpletransform.md
@@ -25,12 +25,13 @@ type of interpolation to be used. Valid values include
 or *simple* interpolation. Returns a new `res` Tensor.
 
 ### [res] image.scale(src, size, [mode]) ###
-Rescale the height and width of image `src`. 
-Variable `size` is a number or a string specifying the 
-size of the result image. When `size` is a number, it specifies the 
-maximum height or width of the output. When it is a string like 
-*WxH* or *MAX* or *^MIN*, it specifies the `height x width`, maximum, or minimum height or 
-width of the output, respectively.
+Rescale the height and width of image `src`.  Variable `size` is a number
+or a string specifying the size of the result image. When `size` is a
+number, it specifies the maximum height or width of the output. When it is
+a string like `WxH` or `MAX` or `^MIN`, `*SC` or `*SCn/SCd` it specifies
+the `height x width`, maximum height or width of the output, minimum height
+or width of the output, scaling factor (number), or fractional scaling
+factor (int/int), respectively.
 
 ### [res] image.scale(dst, src, [mode]) ###
 Rescale the height and width of image `src` to fit the dimensions of 
diff --git a/image-1.1.alpha-0.rockspec b/image-1.1.alpha-0.rockspec
index d0f3e5f..2c498db 100644
--- a/image-1.1.alpha-0.rockspec
+++ b/image-1.1.alpha-0.rockspec
@@ -19,8 +19,7 @@ using Torch's Tensor data structure.
 dependencies = {
    "torch >= 7.0",
    "sys >= 1.0",
-   "xlua >= 1.0",
-   "rational >= 1.0"
+   "xlua >= 1.0"
 }
 
 build = {
diff --git a/init.lua b/init.lua
index 0fc95ab..5a32f9c 100644
--- a/init.lua
+++ b/init.lua
@@ -35,8 +35,6 @@ require 'xlua'
 require 'dok'
 require 'libimage'
 
-local rational = require 'rational'
-
 ----------------------------------------------------------------------
 -- types lookups
 --
@@ -503,7 +501,7 @@ local function scale(...)
                        {type='string', help='mode: bilinear | bicubic |simple', default='bilinear'},
                        '',
                        {type='torch.Tensor', help='input image', req=true},
-                       {type='string | number', help='destination size: "WxH" or "MAX" or "^MIN" or MAX', req=true},
+                       {type='string | number', help='destination size: "WxH" or "MAX" or "^MIN" or "*SC" or "*SCd/SCn" or MAX', req=true},
                        {type='string', help='mode: bilinear | bicubic | simple', default='bilinear'},
                        '',
                        {type='torch.Tensor', help='destination image', req=true},
@@ -512,28 +510,51 @@ local function scale(...)
       dok.error('incorrect arguments', 'image.scale')
    end
    if size then
-      local iwidth,iheight
+      local iwidth, iheight
       if src:nDimension() == 3 then
-         iwidth,iheight = src:size(3),src:size(2)
+         iwidth, iheight = src:size(3),src:size(2)
       else
-         iwidth,iheight = src:size(2),src:size(1)
+         iwidth, iheight = src:size(2),src:size(1)
       end
-      local imax = math.max(iwidth,iheight)
+
+      -- MAX?
+      local imax = math.max(iwidth, iheight)
       local omax = tonumber(size)
       if omax then
-         local sc = rational(omax, imax)
-         height = (rational(iheight)*sc)()
-         width = (rational(iwidth)*sc)()
-      else
-         width,height = size:gfind('(%d*)x(%d*)')()
-         if not width or not height then
-            local imin = math.min(iwidth,iheight)
-            local omin = tonumber(size:gfind('%^(%d*)')())
-            if omin then
-               local sc = rational(omin, imin)
-               height = (rational(iheight)*sc)()
-               width = (rational(iwidth)*sc)()
-            end
+         height = iheight*omax/imax
+         width = iwidth*omax/imax
+      end
+
+      -- WxH?
+      if not width or not height then
+         width, height = size:match('(%d+)x(%d+)')
+      end
+
+      -- ^MIN?
+      if not width or not height then
+         local imin = math.min(iwidth, iheight)
+         local omin = tonumber(size:match('%^(%d+)'))
+         if omin then
+            height = iheight*omin/imin
+            width = iwidth*omin/imin
+         end
+      end
+
+      -- *SCn/SCd?
+      if not width or not height then
+         local scn, scd = size:match('%*(%d+)%/(%d+)')
+         if scn and scd then
+            height = iheight*scn/scd
+            width = iwidth*scn/scd
+         end
+      end
+
+      -- *SC?
+      if not width or not height then
+         local sc = tonumber(size:match('%*(.+)'))
+         if sc then
+            height = iheight*sc
+            width = iwidth*sc
          end
       end
    end