servo: Add a TGA image writer

Source-Repo: https://github.com/servo/servo
Source-Revision: 228c1cf950090c2f53ff3fe58a74bacd096169d5

servo/src/image/encode/tga.rs

@@ -0,0 +1,24 @@
+import gfx::surface;
+import io::writer_util;
+
+fn encode(writer: io::writer, surface: surface::image_surface) {
+    assert surface.format == gfx::surface::fo_rgba_8888;
+
+    writer.write_u8(0u8);                               // identsize
+    writer.write_u8(0u8);                               // colourmaptype
+    writer.write_u8(2u8);                               // imagetype
+
+    writer.write_le_u16(0u16);                          // colourmapstart
+    writer.write_le_u16(0u16);                          // colourmaplength
+    writer.write_u8(16u8);                              // colourmapbits
+
+    writer.write_le_u16(0u16);                          // xstart
+    writer.write_le_u16(0u16);                          // ystart
+    writer.write_le_u16(surface.size.width as u16);     // width
+    writer.write_le_u16(surface.size.height as u16);    // height
+    writer.write_u8(32u8);                              // bits
+    writer.write_u8(0x30u8);                            // descriptor
+
+    writer.write(surface.buffer);
+}
+