What is mono - tiff & png scans rejected as rgb?

[henryg]

I scanned a lot of hand drawings for my daughter's project in mono tiff & png from my Kyocera M5526cdw laser: 600dpi and having selected the monochrome "colour setting" in their app. However, she has been told  that "Some of the images have been saved as Bitmap, whilst others have been saved as RGB, producing compression fuzz around the black lines", and rejected. 

When I look at the image information in Affinity, all show as rgb/8 so I am at a loss at to how/why some are acceptable and others not; and for that matter what is mono? Also, the export & document/convert options only offer RGB 8bit and Greyscale 8bit, adding to my confusion.

Raw data info:

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The images were scanned at different times and I had to recreate the scan profiles as I set up a new pc, so perhaps something went awry. Could setting the scan monochrome "Density" to Auto, which is a option, give rise to the problem? And the original image could be set as "Text", "Text & photo", or "Photo" - I think all scans were done as "Text & Photo"

My daughter worked so hard on this, so your help would be very much appreciated.

 

Henry

[walt.farrell]

1 hour ago, henryg said:

The images were scanned at different times and I had to recreate the scan profiles as I set up a new pc, so perhaps something went awry. Could setting the scan monochrome "Density" to Auto, which is an option, give rise to the problem?

What software are you using to perform the scan?

[NotMyFault]

We would need to get example files uploaded - accepted and rejected ones

 

[thomaso]

3 hours ago, henryg said:

When I look at the image information in Affinity, all show as rgb/8

Affinity doesn't create 1 bit B&W images but converts them into 8 bit RGB for instance if opened in Affinity.

Accordingly the "RAW data info" displayed by Affinity does not necessarily fully correspond with the file. – Instead it may be more reliable to read the EXIF data with another tool e.g. the free "ExifTool". https://exiftool.org/

[loukash]

5 hours ago, henryg said:

When I look at the image information in Affinity, all show as rgb/8

1 hour ago, thomaso said:

Affinity doesn't create 1 bit B&W images but converts them into 8 bit RGB for instance if opened in Affinity.

Exactly.

If you want/need to edit the scans in Affinity for some reasons, you will have to export them as 1-bit PNG.
If set up correctly, the result will be a genuine monochrome bitmap file.

Here's an older video I posted a few years ago on how to convert any image to a 1-bit image. It's been made with Affinity v1, but the process and the export settings are more or less the same in v2.
(The only thing that won't work anymore is the Preview.app conversion from 1-bit PNG to 1-bit TIFF because Apple broke it in recent MacOS versions for good.  So you may need to use a 3rd party app that can handle 1-bit files to convert PNG to TIFF, for example GraphicConverter on Mac. Or an online tool.)

 

[thomaso]

5 hours ago, loukash said:

(…) export them as 1-bit PNG. If set up correctly, the result will be a genuine monochrome bitmap file.

Here's an older video I posted a few years ago on how to convert any image to a 1-bit image.

Good hint/workaround! – But aren't there a few steps too many in your video? I can achieve a 1 bit .PNG just with selecting the export option palettised > black and white  – without the need to a.) change the document colour space/profile, or a need for b.) a threshold adjustment or c.) nearest neighbour' or d.) 'black & white export profile'.

For instance below: A grayscale tiff with alpha placed in a CMYK .afpub and exported as gray/8 with generic gray profile + palettised black & white seems to result in a 1 bit image with only black (no gray) pixels:

[loukash]

11 hours ago, thomaso said:

But aren't there a few steps too many in your video?

Probably. I have originally posted it in another context a few years ago. 
(Disclosure: I'm often "recycling" previously uploaded screenshots and screencasts from my "Other Media → Insert Existing Attachments" forum attachments archive )

[henryg]

I'm trying to get more info, but in the meantime I found that XnView can (batch) convert 8bit tiffs by changing "the colour depth" to binary (B&W?). I'm waiting to hear if the converted files are acceptable which would solve everything, inc hopefully the tears (not mine).

I used Kyocera's Quick Scan program with the output set to monochrome, a "colour setting" hence I suppose the rgb output. I'm a long way out of my comfort zone on understanding this stuff 

I really appreciate all the most helpful comments 

I haven't uploaded any examples as we are still trying to establish which scans are (and are not) acceptable.

[loukash]

2 hours ago, henryg said:

XnView can (batch) convert 8bit tiffs by changing "the colour depth" to binary (B&W?)

Interesting!
Yep, seems to work fine. You can convert to 1-bit TIFF with LZW compression with a single click.  

[loukash]

2 hours ago, henryg said:

Quick Scan program with the output set to monochrome

To get the best results, it's always a better idea to scan in full color and perform any cleanup and conversion later.
In that sense, Affinity Photo offers pretty good tools to "surgically" adjust the monochrome conversion non-destructively, as seen in my screencast.

[henryg]

18 hours ago, loukash said:

To get the best results, it's always a better idea to scan in full color and perform any cleanup and conversion later.
In that sense, Affinity Photo offers pretty good tools to "surgically" adjust the monochrome conversion non-destructively, as seen in my screencast.

That's really interesting. I assume because the maximum data is then collected.

[henryg]

On 4/13/2025 at 5:41 PM, loukash said:

If you want/need to edit the scans in Affinity for some reasons, you will have to export them as 1-bit PNG.
If set up correctly, the result will be a genuine monochrome bitmap file.

AAMOI, I don't see an option in Affinity to export as 1-bit PNG. This is only for my education, as it seems likely the XnView conversion will do the job.

[loukash]

2 hours ago, henryg said:

I don't see an option in Affinity to export as 1-bit PNG

There's no built-in preset (vive la différence), so you can simply save your own preset setting up the corresponding export options manually as seen in my screencast.

3 hours ago, henryg said:

it seems likely the XnView conversion will do the job

I think so.

[henryg]

A big thank you to all that commented/helped. All resolved, and happy daughter.

[influxx]

On 4/13/2025 at 4:24 AM, henryg said:

I scanned a lot of hand drawings for my daughter's project in mono tiff & png from my Kyocera M5526cdw laser: 600dpi and having selected the monochrome "colour setting" in their app. However, she has been told  that "Some of the images have been saved as Bitmap, whilst others have been saved as RGB, producing compression fuzz around the black lines", and rejected. 

When I look at the image information in Affinity, all show as rgb/8 so I am at a loss at to how/why some are acceptable and others not; and for that matter what is mono? Also, the export & document/convert options only offer RGB 8bit and Greyscale 8bit, adding to my confusion.

Hey Henry, just want to clarify a few things for you as it doesnt seem like they have yet. forgive me if I'm treading old ground and insulting your inteligence. Just want to make sure you understand the tech and terms.

When you scan an image the photo sensor can store it in a number of different formats. You will choose which format before you scan, so the sensor knows what it is looking at. A monochrome image scan, as someone mentioned but didnt really explain is a 1 bit image. That means there is only 2 color permutations - on or off, black or white. So there are no grey pixels. Its these 'inbetween' grey pixels that we call anti-aliased in a GREYSCALE image. The soft transition from black to white thru varying numbers of grey tone is what makes an image look natural to use.

Monotone images dont have those grey tones - only black or white - so their edges appear really 'crunchy'. There is no soft transition.

A BITMAP image is an antiquated format from the very dawn of desktop publishing when software and computers were not very fast or clever. We would scan monotone bitmap images at super hi res - like 1200dpi - so we could fake the anti-aliased edges and make the image look very crisp, but not crunchy.

For may many years now these formats have given way to far better tech. First TIFF, then JPEG, now PNG as standard imaging formats for DTP.

To address your problem you would need to go back and scan the images again, and make sure to set the imaging format to GREYSCALE and at least 8-bit, and save into a format like TIFF, JPEG or PNG. Depending on the physical size of the drawings, make sure you scan at a high enough resolution to work with later - at least 200 ppi/dpi

If you'd like to take a screengrab of the scanner software we can walk you thru it if this is all alien to you.

[loukash]

On 4/18/2025 at 11:00 PM, influxx said:

A BITMAP image is an antiquated format from the very dawn of desktop publishing when software and computers were not very fast or clever. We would scan monotone bitmap images at super hi res - like 1200dpi - so we could fake the anti-aliased edges and make the image look very crisp, but not crunchy.

For may many years now these formats have given way to far better tech. First TIFF, then JPEG, now PNG as standard imaging formats for DTP.

To address your problem you would need to go back and scan the images again, and make sure to set the imaging format to GREYSCALE and at least 8-bit, and save into a format like TIFF, JPEG or PNG. Depending on the physical size of the drawings, make sure you scan at a high enough resolution to work with later - at least 200 ppi/dpi

Um… uh… sorry, but… no.
Because as always:

1. It depends.®
2. Context matters.™

[NotMyFault]

While we really appreciate posts giving good explanations, the latest one mixes up several topics which are interrelated, but not in the way the posts stated.

we must carefully distinguish 

• File formats (like BMP or tiff) and their ability wrt. Color formats, profiles, color channel bit depths, compression
• color formats
  • Pure black / white (meaning 1 bit color channel depth)
  • greyscale (typically 8 bit color depth, sometimes 16 or 32)
  • RGB (typically 3 color channels, or 4 including alpha)
• methods to store image data
  • plain (device encoding, light CRT displays or printers)
  • gamma encoded (the standard in sRGB since >40 years)
  • linear gamma (better linear, as gamma = 1.)
  • log or PQ transfer functions (introduced for HDR video and images)
  • palettized images (using 8 bit index to a color palette out of more, up to 16,7 mio), often combined with dithering to counteract loss of color channel depth
• dithering (method to create illusion of many color shades from small number of colors, swapping image resolutions vs. Color resolution)
• Anti-aliasing (method to visually soften harsh edges of vector objects like fonts/chatacters when rendered into a pixel grid)

alls these factors play a role, but your conclusion

10 hours ago, influxx said:

A BITMAP image is an antiquated format from the very dawn of desktop publishing when software and computers were not very fast or clever. We would scan monotone bitmap images at super hi res - like 1200dpi - so we could fake the anti-aliased edges and make the image look very crisp, but not crunchy.

For may many years now these formats have given way to far better tech. First TIFF, then JPEG, now PNG as standard imaging formats for DTP.

may hurt the feelings of many forum users who use the technology and methods you rate as antiquated and clearly object to that part.

I personally don’t get what you want to explain with that sentence, specifically with the (dis-valuation) of certain aspects. 

1. using higher res is no solution for every problem. Just in contrast, the „megapixel war“ of the 2000 years caused so many issues with cheap bad scanner and camera sensors lacking DR and basic quality, interpolating internally and giving bloated high megapixel mushy images.
2. i really don‘t which of the two scans of the OP showed artifacts. I only know the scanning went wrong as different settings where used for the scans. It is still open if a highres pure BW scan or or lower res greyscale scan is what is expected by the recipients. I can only assume that the RGB scan was exported as jpeg in low quality leading to compression artifacts. If that step was corrected (save in RGB, but use higher compression or save lossless compressed as tiff) may solves the issue, unrelated to BW / greyscale / color and scan resolution

[NotMyFault]

@influxx your last reply to loukash was attacking him on personal level (without any reason), against the forum rules.

please adhere to the forum guidelines. We are happy to have a pointed professional discussion with you, but will not tolerate personal attacks.

[thomaso]

10 hours ago, influxx said:

Its these 'inbetween' grey pixels that we call anti-aliased in a GREYSCALE image. The soft transition from black to white thru varying numbers of grey tone is what makes an image look natural to use.

This may mislead / depend, too. In a grayscale image gray pixels aren't usually related to antialiasing. Even on scans of hand drawings, as in the OP's example, gray (not black) may appear at the stroke's edges, both in the original and its scan and without any antialiasing.

10 hours ago, influxx said:

Monotone images dont have those grey tones - only black or white - so their edges appear really 'crunchy'. There is no soft transition.

Also this thought may confuse or depend. It was/is the sense of the higher resolution (e.g. 1200 DPI) of black-and-white scans or images to enable gradients and/or tints brighter than pure black in combination with dithering.

An advantage of this method (1 bit) was/is for instance the ability to print a visual impression of half tone without requiring an additional print screen (e.g. grid of dots).

A visual example of this method (1 bit) was/is shown in the screenshot of this previous post above.

[Alfred]

10 hours ago, influxx said:

insulting your inteligence

*intelligence [two els]

 

10 hours ago, influxx said:

A monochrome image scan, as someone mentioned but didnt really explain is a 1 bit image.

 

10 hours ago, influxx said:

Monotone images [don't] have those grey tones

Monotone black images are 1-bit, monochrome black images are greyscale (i.e. more than 1 bit, usually at least 8).

[loukash]

45 minutes ago, Alfred said:

Monotone black images are 1-bit, monochrome black images are greyscale (i.e. more than 1 bit, usually at least 8).

Thanks for clarifying. I've also used the term incorrectly in a post above.

[NotMyFault]

3 hours ago, Alfred said:

Monotone black images are 1-bit, monochrome black images are greyscale (i.e. more than 1 bit, usually at least 8).

I never heard this definition before. It makes some sense if taken literally, but Monotone and Monochrome could be misinterpreted easily as monotone in common language has a different meaning.

I would prefer the definition below to resolve any ambiguity:

• binary B&W images or binary colors
• greyscale images or greyscale colors. 

 

[Bound by Beans]

1-bit is still used today – though I don’t work with it personally more – in a few specific contexts, such as archival work (for storing clean, high-contrast scans of technical drawings or old documents, the files become extremely small and easy to search through), OCR systems (where simplified black-and-white images can improve character recognition  speed and accuracy), and laser engraving or CNC workflows (where black denotes areas to cut or engrave, and white means skip). It also appears in certain embedded systems (like simple screens on appliances or instruments, where memory and power efficiency matter).

That said, I’m not sure how much real-world need Affinity users actually have for supporting this format. Maybe for things like scanning and cleaning up technical drawings, old documents, or line art that needs to be kept lightweight and very sharp. Possibly also for prepping artwork for laser cutting or engravings, where clean black-and-white paths are needed. I used monochrome scanning myself for drawings intended for vector tracing and hand tracing, where I preferred the format, but it's been a while now. In any case, one should not underestimate how much something is used, regardless of how much it has disappeared from one's own daily routine. I can mention that fax machines and typewriters are still in use—for various reasons, such as security. One shouldn't phase out something before being certain about its replacement.

I also believe that "monotone" is a term sometimes used to refer to 1-bit images, but it doesn't actually describe them accurately. "Monotone" technically refers to something uniform in tone or lacking variation, which in a linguistic or musical context makes sense. However, when used about images, it’s imprecise, because a 1-bit image isn't just visually flat—it’s literally binary, with only two values: black or white. There's no tonal range, no gradient, just on or off. The correct term in this context is "monochrome," which means one color and is more appropriate for describing the binary nature of 1-bit images.

The industry should stick to using “monochrome,” as it’s the correct and standardized term—also recognized by ISO*—for describing 1-bit black-and-white images. “Monotone” isn’t technically accurate and has no formal standing in imaging terminology. I believe it's also mentioned in the DICOM and Netpbm documentation.

*ISO/IEC 8632:1999, which defines the Computer Graphics Metafile (CGM) format, specifies "monochrome" for images that consist of a single color on a contrasting background.

 

[NotMyFault]

26 minutes ago, Bound by Beans said:

The correct term in this context is "monochrome," which means one color and is more appropriate for describing the binary nature of 1-bit images.

I can’t agree to this sentence (the remainder of you post I agree).

monochrome includes chrome, meaning chroma, meaning color. It allows shades of that color, meaning greyscale. So I really object using monochrome for binary BW images.

i know it might be used without ever marking that intention, but this increases ambiguity.

Probably something happen similar to „Quantensprung“, a phrase going back to Ferdinand Piëch, who used it to express a big step in automotive technology (or marketing), whereas the actual meaning in physics (where it was lent from) means the minimal possible jump, and there is no smaller jump possible - so completely the opposite.

[loukash]

34 minutes ago, Bound by Beans said:

I’m not sure how much real-world need Affinity users actually have for supporting this format.

Given that more than 90% of all Affinity customers *) don't even have an account on this forum, we'll likely never know for sure.
*) The math: It's been officially communicated that there are over 3,000,000 Affinity licenses sold, and this forum has 210,437 registered members as of today

2 hours ago, NotMyFault said:

monotone in common language has a different meaning

Quote

monotone | BrE ˈmɒnətəʊn, AmE ˈmɑnəˌtoʊn | 

A noun

1 gleich bleibender Ton 

2 (uniformity) (general) Einerlei (Neutr.) (of colour) Einfarbigkeit (Fem.) (of style) Monotonie (Fem.) 
▸ grey monotone
graues Einerlei 
▸ engravings in monotone
einfarbige Stiche 

B adjective 

1 (monotonous) eintönig, monoton ‹Geräusch, Sprache, Akzent, Rezitation› 

2 (in one colour) einfarbig

from: Oxford German Dictionary, Copyright © 2008, 2021 Oxford University Press. All rights reserved.

(emphasis mine)