I just tried to remove something from a picture by using the online filter Inpaint [patch based]. I painted the unnecessary object with the same red color(255/100/100) used by the filter and after loading the image - not altering any of the default settings - clicked on "render full image" then download. But the image didn't change at all... So what might I've done wrong? Even if didn't expect the object to be covered perfectly because it is in the middle of two very different image halfs I would expect SOME covering...

only two comments:
1-red should be 255 0 0
2-to paint you should use pencil (brush with hard edge) not pen

My fault, it is 255/0/0 in both cases, I've looked at the wrong values in both cases. You are right with the pencil but even though the outer borders are wrong color, the inner part should be correct and should produce at least a slight result. I've redone the picture with a hard pencil - but the result is the same, nothing changes.

[Several investigative minutes later]
I have found the reason! I had used the online editor from Pixlr to create the red mask on the picture. I carefully chose the color 255/0/0, used the pencil and saved the image as jpg to disk, then used it with GMic online. Meanwhile I've started Gimp and tested it. In Gimp the Inpaint color dialog offers a color picker. So I opened the picture I edited with Pixlr and used the color picker on the red. And guess what - it sais 254/0/0 and 255/1/0! So I guess the color got corrupted by saving as JPG.

I get a perfect result when I use Gimp to create the red mask and the use the G'Mic plugin. I even don't get a perfect result when I use the Pixlr editor with a pencil and when I save as PNG - so I guess the problem was a) using JPG to save before letting G'Mic do its work and b) the Pixlr pencil is not that color exact on the edges...

BTW: Weird in the online version is that I only get Inpaint [patch based] when I click on Inpaint [holes], all filters seem to be displaced by one.

Weird too, the online version of Inpaint [patch based] seems to work different? I have used the same values in the two pictures. The one with the red marks was created completly online. Though the red mask was not that perfect I wonder why the filling is different... especially in the sky.

Only can use a hard brush (no grayscale in the brush; see what I mean below).

@lylejk: Yes, I know. But the hard brush (pencil) in Pixlr obviously is not 100% hard and JPG is a lossy format so that it might come to slight color differences when saving.

Just tested it again online, now [patch based] is [patch based] again, fine, whatever caused the displacement. And it also renders the image correctly now, no green in the sky anymore...