prototype

Author: DanielJDufour

.gitignore

@@ -102,3 +102,6 @@ dist
 
 # TernJS port file
 .tern-port
+
+data/LC*
+data/.DS_Store

README.md

@@ -1,2 +1,29 @@
+:warning: This package is under development.  Please report an issues here: https://github.com/geotiff/is-cog/issues
 # is-cog
 Super Light and Fast Method for Checking if a TIFF is a Cloud Optimized GeoTIFF
+
+# how does it work
+1. It uses [id-tif](https://github.com/DanielJDufour/id-tif) to check if the file is a TIFF. 
+2. If it is a TIFF, it uses [is-geotiff](https://github.com/GeoTIFF/is-geotiff) to check if the file is a GeoTIFF.
+3. If it is a GeoTIFF, it checks if the bytes associated with the following tags are present: TileWidth, TileLength, TileOffsets, and TileByteCounts.
+
+# install
+```bash
+npm install is-cog
+```
+
+# usage
+```js
+const fs = require("fs");
+const isCOG = require("is-cog");
+
+const buffer = fs.readFileSync("./landsat_scene.tiff");
+
+const { is_cog, is_geotiff, is_tiff } = isCOG({
+    data: buffer,
+    debug: false // set debug to true for increased logging
+});
+// is_cog is true
+// is_geotiff is true
+// is_tiff is true
+```

data/cog.tif

@@ -0,0 +1,3 @@
+#!/bin/sh -e
+
+wget https://landsat-pds.s3.amazonaws.com/c1/L8/024/030/LC08_L1TP_024030_20180723_20180731_01_T1/LC08_L1TP_024030_20180723_20180731_01_T1_B4.TIF

data/flower.jpg

@@ -0,0 +1,36 @@
+const idTIF = require("id-tif");
+const isGeoTIFF = require("is-geotiff");
+const hasBytes = require("has-bytes");
+
+module.exports = function isCOG({ data, debug, is_geotiff, is_tiff }) {
+  if (debug) console.log("[is-cog] starting with data", data);
+
+  if (is_tiff === undefined) is_tiff = idTIF(data, debug);
+
+  // return early if not a TIFF file
+  if (!is_tiff) {
+    if (debug) console.log("file is not a tiff, so returning early");
+    return { is_cog: false, is_geotiff: false, is_tiff };
+  }
+
+  if (is_geotiff === undefined) is_geotiff = isGeoTIFF({ data, debug }).result;
+
+  // return early if not a GeoTIFF file
+  if (!is_geotiff) {
+    if (debug) console.log("file is not a geotiff, so returning early");
+    return { is_cog: false, is_geotiff, is_tiff };
+  }
+
+  const { result } = hasBytes({
+    data,
+    debug,
+    sequences: {
+      TileWidth: [66, 1], // 0x0142
+      TileLength: [67, 1], // 0x0143
+      TileOffsets: [68, 1], // 0x0144
+      TileByteCounts: [69, 1] // 0x0145
+    }
+  });
+
+  return { is_cog: result, is_geotiff, is_tiff };
+};