Upon close inspection the image contains a dog holding an object with very lightly colored text. Opening the image file in a basic image editor such as Paint.NET, Photoshop, or Gimp and adjusting the contrast, saturation, and/or hue of the image would make the flag appear as tjctf{th3_f0x_jump3d_0v3r_m3}

Original writeup (https://github.com/tjgerot/write-ups-2016/tree/master/tjctf-2016/doge1-30).