The file's DPI does not matter. DPI is only important when printing the file. If, for example, your file is 1024x1024 and you set the DPI to 1024, the image will only be 1 inch square on the paper when printed. If you set the DPI to 128, the printed image would be 8 inches square. Even though the printed size has changed, the file is still only 1024x1024 pixels.