The bucket fill has two modes: Fill whole selection, and Fill similar colors and . With the first mode it abides to the selection. With the second it ignores the selection (see that second mode as being a combined Select by color+Bucket-fill selection).
Since you are using that Fill similar colors option, with a large threshold to boot, the Select by color part selects about everything (and is sensitive to where you click...).
IMHO what you want is:
Since you are using that Fill similar colors option, with a large threshold to boot, the Select by color part selects about everything (and is sensitive to where you click...).
IMHO what you want is:
- Color select the white spots
- Invert the selection
- Bucket-fil the selection