Mon 21 Jul 22:43:21 CEST 2025

js/x11/examples/smoketest/bmp.js

@@ -0,0 +1,45 @@
+// http://atlc.sourceforge.net/bmp.html
+// Any better format documentation?
+
+var fs = require('fs');
+var Pixmap = require('./pixmap').Pixmap;
+var Buffer = require('buffer').Buffer;
+require('../../lib/unpackbuffer').addUnpack(Buffer);
+
+var reversed = new Buffer(256);
+for (var i=0; i < 256; ++i)
+{
+    var res = 0;
+    for (b = 0; b < 8; ++b)
+    {
+        res += ((i & (1 << b) ) >> b) << (7-b);
+    }
+    reversed[i] = res;
+}
+
+module.exports.decodeBuffer = function(buffer)
+{
+    var h = buffer.unpack('CCLxxxxLLLLSSLLLL');
+    var header = {};
+    header.filesize = h[2];
+    header.data_offset = h[3];
+    header.header_size = h[4];
+    header.width = h[5];
+    header.height = h[6];
+    header.num_planes = h[7];
+    header.bpp = h[8];
+    header.compression = h[9];
+    header.data_size = h[10];
+    header.hresolution = h[11]; // pixels per METER!
+    header.vresolution = h[12];
+    // skipped: num colors, num important colors, palette
+    var data = buffer.slice(header.data_offset, header.data_offset+header.data_size);
+    // TODO: decode compressed bitmap
+    //console.log(header);
+
+    // mirror bits & invert
+    for (var i=0; i < data.length; ++i)
+        data[i] = 255 - reversed[data[i]];
+
+    return new Pixmap(header.bpp, header.width, header.height, data);
+}