Make readme more concise

README.md

@@ -11,106 +11,22 @@ let colormap = require('colormap')
 
 let colors = colormap({
     colormap: 'jet'
-    nshades: 72,
+    nshades: 10,
     format: 'hex',
     alpha: 1
 })
 ```
 
 ## API
 
-### colormap(options)
+### list = colormap(options?)
 
-| Property | Default | Meaning |
-|---|---|---|
-| `colormap` | `'jet'` | Color scale name |
-| `nshades` | `72` | Number of colors in returned array |
-| `format` | `'hex'` | `'hex'`, `'rgbaString'`, `'rgb'` |
-| `alpha` | `1` | Alpha range, can be an array with alpha values or just 2 values for start/end colors. |
-
-where leaving `options = {}` or `undefined` results in the defaults given above. There is a minimum number of `nshades` divisions you can select since the algorithms for each colormap have different requirements. `colormap` throws an error if there are too few divisions for the chosen colormap and gives the minimum number required. You should be safe with `n > 10` for all the colormaps, though some require much less (much simpler to implemenent).
-
-## Options
-The `colormap` option can be any of the supported builtin colormaps. Or you can add your own. For an example of how to add your own see the json format available at:
-
-```javascript
-colorscales = require('colormap/colormap')
-```
-
-Colorscales are a sequence of objects containing an `index` and `rgb` key. The index defines how fast or slow the `rgb` values will change from one segment to the next. Ie.the steepness of the gradient between two segments. The `rgb` parameter can hold a length 3 or 4 array, depending if alpha values are included in the mapping.
-
-## Return values
-An array of hex values ('hex') or an array of length 4 arrays containing rgba values ('rgb') or an rgba css string ('rgbaString').
-
-## Complete Example
-This example will produce the colormap image used at top of this README. It uses all built in color maps and utilizes alpha channel mapping.
-
-```javascript
-var cmap = require('./..'),
-    canvas = document.getElementById('canvas'),
-    img = document.getElementById('background'),
-    c = canvas.getContext('2d'),
-    n = 48,
-    colormaps = [
-        'jet', 'hsv','hot','cool','spring','summer','autumn','winter','bone',
-        'copper','greys','YIGnBu','greens','YIOrRd','bluered','RdBu','picnic',
-        'rainbow','portland','blackbody','earth','electric'
-    ];
-
-img.onload = run;
-
-function drawColorMaps (colormap, name, height) {
-    /*
-     * Build up the color ranges and add text
-     */
-    for (var j = 0; j < n; j++) {
-        c.fillStyle = colormap[j];      // start ind at index 0
-        c.fillRect(j*10, height, 10, 40);
-
-    }
-    c.fillStyle = '#262626';
-    c.font = '16px Helvetica';
-    c.fillText( name, n*10 + 10, height + 26);
-}
-
-function run() {
-    var height, colormap;
-    c.canvas.height = colormaps.length * 40 + img.height;
-    c.canvas.width = 648;
-
-    for (var i = 0; i < colormaps.length; i++) {
-        height = i*40;
-        colormap = cmap({
-            colormap: colormaps[i],
-            nshades: n,
-            format: 'rgbaString'
-        });
-        drawColorMaps(colormap, colormaps[i], height);
-    }
-
-    /*
-     * Now lets try some alpha maps overtop an image!
-     */
-    var ilast = i;
-    c.drawImage(img, 0, i*40, 480, 240);
-
-    // remove background img
-    img.parentElement.removeChild(img);
-
-    for (var i = 0; i < colormaps.length; i++) {
-        height = (ilast + i)*40;
-        colormap = cmap({
-            colormap: colormaps[i],
-            nshades: n,
-            format: 'rgbaString',
-            alpha: [0, 1]
-        });
-        drawColorMaps(colormap, colormaps[i] + ' with transparency', height);
-    }
-}
-```
-
-Then just [browserify](https://github.com/substack/node-browserify) it and throw it in some html and it will output the image above!
+Property | Default | Meaning
+---|---|---
+`colormap` | `'jet'` | Color map name from the image above or a custom color scale — a sequence of `{index, rgb}` objects, where index is `0..1` number and `rgb` is a length 3/4 array with values for the color stop.
+`nshades` | `72` | Number of colors in returned array, the minimum number depends on `colormap`.
+`format` | `'hex'` | `'hex'` for `#aabbcc`, `'rgbaString'` for `rgba(255, 255, 255, 1)`, `'rba'` for `[255, 255, 255, 1]`, `'float'` for `[1, 1, 1, 1]`.
+`alpha` | `1` | Alpha range, can be an array with alpha values or just 2 values for start/end colors. |
 
 
 ## Credits

index.js

@@ -119,11 +119,20 @@ function createColormap (spec) {
     colors.push(cmap[cmap.length - 1].rgb.concat(alpha[1]))
 
     if (format === 'hex') colors = colors.map( rgb2hex );
-    if (format === 'rgbaString') colors = colors.map( rgbaStr );
+    else if (format === 'rgbaString') colors = colors.map( rgbaStr );
+    else if (format === 'float') colors = colors.map( rgb2float );
 
     return colors;
 };
 
+function rgb2float (rgba) {
+    return [
+        rgba[0] / 255,
+        rgba[1] / 255,
+        rgba[2] / 255,
+        rgba[3]
+    ]
+}
 
 function rgb2hex (rgba) {
     var dig, hex = '#';