cmpimg: invalid handling of images that are not image.RGBA

[sbinet]

in cmpimg, one sees:

func cmpImg(v1, v2 image.Image, delta float64) bool {
        img1, ok := v1.(*image.RGBA)
        if !ok {
                img1 = newRGBAFrom(v1)
        }

        img2, ok := v2.(*image.RGBA)
        if !ok {
                img2 = newRGBAFrom(v2)
        }

        if len(img1.Pix) != len(img2.Pix) {
                return false
        }

        max := delta * delta
        bnd := img1.Bounds()
        for x := bnd.Min.X; x < bnd.Max.X; x++ {
                for y := bnd.Min.Y; y < bnd.Max.Y; y++ {
                        c1 := img1.RGBAAt(x, y)
                        c2 := img2.RGBAAt(x, y)
                        if !yiqEqApprox(c1, c2, max) {
                                return false
                        }
                }
        }

        return ok
}

it may happen that v2 isn't a *image.RGBA.
in that case, ok==false and we convert v2 into img2 going through the necessary steps.

and if no pixel differed too much between img1 and img2, we return ok... which is still false.

[kortschak]

ooops

[sbinet]

yeah... silly mistake, heh?

looking at the coverage of cmpimg.go, it would perhaps stand to reason to improve it a little bit.
WDYT?

[kortschak]

SGTM