How to use
- Open the bars.
- Expect 32 by 16 gray.
- Open the tile and expect 48 by 48 gray.
Formula / how it works
The bars are 32 by 16 in colour and 32 by 16 after the gray filter. The tile is 48 by 48 both before and after. Colour is discarded. The gray PNG does not keep a colour version alongside it. A red half and a blue half become two grays, and they may be close if their luminance was close. The page does not claim a printer profile. It uses the browser grayscale filter. Metadata is not copied. A GIF animation contributes one frame. Use the colour file if you still need the red and the blue.
32 by 16 and 48 by 48 are the proof the filter does not resize. The red and blue halves become grays. If those grays are hard to tell apart, that is luminance, not a bug, and the colour file is the one to keep. Metadata does not come along. One GIF frame would be gray. The rest of an animation would not.
The bars stay 32 by 16 and the tile stays 48 by 48, which is how you know the filter did not resize. Colour is gone. Two grays may be hard to separate if the red and the blue had similar lightness, and that is a reason to keep the colour file rather than a bug report. No printer profile is applied. Metadata is not copied. An animation would contribute one frame. The browser did the filter locally.
32 by 16 and 48 by 48, colour discarded, no resize. If the two grays are hard to tell apart, keep the colour file. No printer profile. No metadata. One animation frame at most. The filter ran in the browser.
Compare the colour bars with the gray bars at the same 32 by 16 before you replace the colour file. Do the same with the 48 pixel tile. If the two grays are muddy, the colour file was the point. No profile, no metadata, no extra frames. The filter is local. The download is a new PNG. The picture you opened is still colour on disk.
Keep the colour bars until you have looked at the gray ones at 32 by 16, and keep the colour tile until you have looked at 48 by 48 gray. Similar grays mean the colours had similar lightness. That is not a resize bug. There is no profile and no metadata in the download. An animation would lose every frame but one. The colour original stays on disk. Similar grays are a reason to keep that colour file, not a reason to call the 32 by 16 or 48 by 48 result a resize. Keep the colour file until the gray one is the picture you meant to publish. The bars and the tile keep their pixel sizes, 32 by 16 and 48 by 48, which is the proof the filter did not resize either file. Publish the gray PNG only after you have compared it with the colour original.
Add a frame afterwards with image border.
Worked examples
Gray bars
Inputs: igr-f: bars-32x16.png
On this page, take bars-32x16.png and press Make grayscale. Colour is discarded and the pixel size stays.
Result: Grayscale PNG: 32×16. Colour is discarded. Size in pixels stays the same. 0.1 KB
Gray tile
Inputs: igr-f: tile-48.png
On this page, take tile-48.png and press Make grayscale. Colour is discarded and the pixel size stays.
Result: Grayscale PNG: 48×48. Colour is discarded. Size in pixels stays the same. 0.2 KB
Use cases
- Dropping colour without resizing.
- Keeping a PNG.
- Leaving metadata behind.
- Using one GIF frame only.
Tips & limitations
- Red and blue become grays.
- The size does not change.
- There is no colour copy hidden in the file.
- The browser filter is the method.
FAQ
Did the bars change size?
No. Still 32 by 16.
Did the tile change size?
No. Still 48 by 48.
Is colour kept in a side channel?
No. It is discarded.
Which filter?
The browser grayscale filter.
Is a profile applied?
No printer profile is claimed.
Is the file uploaded?
No.
The two grays may look similar if the red and blue had similar luminance. The colour file is the one to keep if that matters.