e-shuushuu forums

When I try to upload a bitmap image it says "Error: This file is not an image!"

Probably an image file with wrong file extension, btw dont upload BMP image files, just recompress it to png.
BMP images are generally uncompressed, the file size is much larger than compressed image format like jpeg and png.

I knew that BMP images weren't uploadable for some time now. Making this into a bug report kind of surprises me O_o Since, well .. it's not a bug in the first place.

Well, the traditions page does say that they can be uploaded. We should fix that.

I recommend against it, there is zero reason to use BMP. Convert it to PNG and it will actually have a lower filesize and identical quality. Only a complete fool who knows nothing of filetypes would upload one.

I agree with Quenlin. That's why you don't see a lot of .bmp images. If not rarely or at all. But I have to say that half of them that save as .jpg / .jpeg without the right configurations (as in it being a high quality image, like the .png one) are just not interested in the quality or plain dumb.
Start "Paint", open the .bmp image and then "Save as..." a .png image. Don't be lazy.

Not every image editor are equals when it comes to saving to PNG, so I advise to avoid Paint. irfanview provide a good PNG compressor if that's what you only need.

Paint handles PNG just fine really, now jpg on the other hand... oh lord.