May 2014 Essay - Pixel-Based Graphics and Resolution

[Barbara B]

Pixel-Based Graphics and Resolution




This month Gary has substituted an essay for the regular tutorial because it’s just too important for artists to get their heads around the very real differences between vector and bitmap graphics. Considering 98% of web content is pixel-based, you might want to get to know pixels a little bit better.

In Gary’s essay, he takes you through image resolution in a way that applies to Xara and your work, and by the time you’re done reading, you’ll be able to start drawing with a new perspective and more confidence that What You Draw is What Your Audience Will See (WYDIWYAWS, or something like that). Read it now!

Let’s discuss this stuff in this thread when you’re done reading.

[theinonen]

I believe BMP image format actually will support image resolution.

[mwenz]

Thanks, Gary!

Your essay highlighted one of the things I dislike about Xara product's handling of image files (exporting especially, but importing too). Because Xara products are hard-wired to use the DPI field (and I hate this abused designator) when exporting an image type it has caused people much confusion. If and when I export an image for web usage, I wish that field wasn't even there (or used internally). All that matters for the web are the pixel dimensions.

The so-called DPI entry in an image file's header really has no bearing, even for print. It is an aid for application to size an image upon import...which I could care less about anyway.

[Gare]

I believe BMP image format actually will support image resolution.

To theinonen and all readers: my apologies for a grievous error in my writing. Theinoneon is correct: the Windows BMP file format can support image resolution, and I've rewritten the part of my essay to address this error.

It can support image resolution, but frequently BMP images default to 96 pixels/inch because of the way the programmer has written the program to export the file, so let me stress that BMP has a largely unexploited capability to hold image resolution. MS Paint, for example, doesn't have rulers, and it doesn't offer resolution settings for exporting images. Microsoft migrated to PNG as their de facto file format for the UI several years ago, and BMP is an openly published standard, so it probably won't go away, but it just doesn't have the impetus behind it that other file formats do.

Please excuse my moment of cranial flatulence in writing that section, and I've expanded it a little. Did you know BMP can also support an alpha channel? Macromedia used to exploit this and I know of few other programs that can read the alpha channel embedded in a BMP.

I suggest you try TIFF, PNG, PSD, and JPEG for Xara exports as bitmaps. Even though Xara exports images to the sRGB color space and there's no way I can see that this can be changed, at least it's exports have a color space tagged to them.

I do not believe BMP images can accept color space tagging. It's just a file format, like the Macintosh PICT file, that served a valuable purpose in the early 1990s, but has been largely usurped by more flexible and capable image file formats.

Thanks again for pointing out my mistake, theinonen,

My Best,

Gary

[Gare]

Thanks, Gary!

Your essay highlighted one of the things I dislike about Xara product's handling of image files (exporting especially, but importing too).

You're welcome, Mike, and I was not out to bash Xara in this essay, but rather to explain the way things can be done—based on some principles I think I explained—to get your bitmap work out correctly from Xara.

For me, the mind-blowing discovery when I was researching for the essay is that qualitatively, a screen snag of a bitmap image in Xara is smoother and at the same tiome provides more legibility of reduced text in a bitmap image than Photoshop does.

Different algorithms, and as I mentioned, early on, Xara's screen display engine was tweaked to perfection. Illustrator didn't have anti-aliasing, CorelDRAW didn't anti-alias to screen. Even though the first version didn't have a print engine, your work was always a joy to behold onscreen, it just looked better than any other drawing program, and it exported to bitmap file format the same way.

We just need to understand anti-aliasing and resolution a little better as designers (like myself) tend to be not as technically concerned as we should be. My first Photoshop work back when version 2.5 came out for ?Windows looks like crap when I veiw it today because I didn't grok monitor calibration, file formats, color capability, color spaces, and that jazz.

I don't want Xara users to look back in regret at spoiled, saved work the way I do with Photoshop!

My Best,

Gary

[mwenz]

...I suggest you try TIFF, PNG, PSD, and JPEG for Xara exports as bitmaps. Even though Xara exports images to the sRGB color space and there's no way I can see that this can be changed, at least it's exports have a color space tagged to them...

Though JPG can support CMYK, Xara products don't (and I could care less). But TIF does.

Mike

[Gare]

Hi Mike—

We're referring to apples and oranges here. Yes, Xara can export to CMYK, but CMYK is sort of a color mode and not a color space. sRGB defines the extent of expressable colors regardless of the "domain" of the colors. Xara presumes sRGB when exporting to an RGB color space, and there are lots of different color spaces with different overlapping areas.

CMYK defines a structure for a bitmap document. For example, in CMYK mode, you get red by mixing yellow with magenta in a subtractive color fashion, counter-intuitive to simpletons such as I. CMYK also has a color space, an expressable range of colors outside of which cannot be reproduced.

And yes, though: TIFF and PSD are the only two bitmap file formats that will accept CMYK color mode when you export from Xara. Correct me, anyone, if there's a 3rd or 4th.

The point I was hinting at but didn't directly mention is that because when you're dealing with the RGB color space, of which sRGB is a subset, you'd better'd be prepared, if you're using Photoshop or other program that recognizes tagged color profiles, to have a document set up to sRGB and not Adobe RGB (1998), because if you copy a bitmap from Xara to the Clipboard and paste into a default document in Photoshop, the colors will be overly saturated and too bright. This is the act of mismatched color profiles (color spaces).

Yep, CMYK has its own color space, but I wasn't getting at color modes in the essay. I mentioned sRGB as a "by the way", and color space would be an article in and of itself. That and color tagging color profiles.

But as long as you brought it up, here's a graph I made a long time ago. When converting from one color space to another, it's best to use CIELAB color space as the "container"; it's larger than other common color spaces, so clipping doesn't occur when you go, for example, from sRGB to CMYK color space.



It this stuff boring people?

Seriously: I wanted a higher level discussion for this part of tg than what a tool does, for once. :)

Output and export accuracy makes it possible for your Xara work to look the same when translated to a different digital file format and structure.

-g

[mwenz]

...We're referring to apples and oranges here. Yes, Xara can export to CMYK, but CMYK is sort of a color mode and not a color space. sRGB defines the extent of expressable colors regardless of the "domain" of the colors.

Yes, I know.

My mentioning the CMYK was in part because of

I suggest you try TIFF, PNG, PSD, and JPEG for Xara exports as bitmaps. Even though Xara exports images to the sRGB color space and there's no way I can see that this can be changed, at least it's exports have a color space tagged to them.

And further...

Xara presumes sRGB when exporting to an RGB color space, and there are lots of different color spaces with different overlapping areas...

Xara products have no real concept of color space except in a generic sense. There is no color space tagging when exporting either RGB or CMYK image formats. So the point is moot, me thinks.

Now, should Xara (the company) ever decide to allow exporting tagged images...but even more importantly, honoring/using tagged images coming into it...that would be great. As it is, Xara products disregards any color space profiles.

In conjunction with the color spaces (import/export, etc.), Xara (the company) needs to also get rid of the so-called "Simulate print colors" and replace it with color management altogether, and to more reasonably display the color intent on-screen. The only way I can think of this working is if they follow Adobe, Quark, Corel, etc., and have document color modes.

[Gare]

Agreed, Mike.

I realized early on that Xara is defaulting to sRGB when no profiling is offered, I asked about it, and Xara I believe was originally touted as the perfect Web graphics suite back when Corel licensed it as CorelXara. So it makes sense—whether it applies today or not—that Xara defaults to the W3 agreed-upon color space of the web, no?

This is a good to bring these points up, but you and I really have no discussion going on because we're in agreement, man! ;)

I'll bop over to "Dear Xara" and file our paperwork, eh?

If anyone is still flummoxed by image resolution, I'd be happy to expand upon it here.

My Best,

Gary

[theinonen]

I do not believe BMP images can accept color space tagging. It's just a file format, like the Macintosh PICT file, that served a valuable purpose in the early 1990s, but has been largely usurped by more flexible and capable image file formats.

Actually user manual for the scanning software I use says they can but Windows 5 header is required for an embedded profile. No way to test though as the .bmp files that the software will output have Windows 3 header.