Newbie somewhat confused, needing some basic pointers

[artistgrrl]

Hi All,

I am a newbie and even though I've been studying the XnView help files, I'm already confused. I am a photographer and I also dabble in fractals and other abstract art. I was getting concerned about the looks of my fractal art especially; in them I can see some obvious loss of quality when they are converted from BMP to JPG files. I was advised to begin with XnView for image resizing, and also to install RIOT as a plugin, to be used for final conversion to JPG. On some of my images I would rather leave the file at large dimensions to show more detail. However I am concerned about massive file sizes such as we get with the formats I mention. I see that images can be converted to PNG with XnView. I am hoping to reduce the "weight" of the files. But what would be the ideal procedure and the correct settings to lighten up the files and yet retain as high image quality as possible? - whether the final result is PNG or JPG? As you can see, I just need a little guidance here... Thank you!

[XnTriq]

Welcome to the forum, artistgrrl

I'd say you should start by converting your BMPs to PNGs.
This will drastically reduce the size of your images without any sacrifice in quality, because PNG is a lossless format.

Here are the results of my tests with MyFirstFractal.bmp (3,686,494 bytes):

• 1,443,956 bytes = Ulead SmartSaver
  1,441,060 bytes = Paint Shop Pro (PNG » optimizer export)
  1,431,520 bytes = XnView (PNG compression level 9)
  1,431,499 bytes = Photoshop + SuperPNG
  1,375,747 bytes = XnView + RIOT add-on
  1,341,454 bytes = I****View + PNGOUT
  1,267,339 bytes = PngOptimizer

Related topics:

• RIOT — Radical Image Optimization Tool
• RIOT Plugin Installer
• RIOT plugin for dummies
• PngOptimizer (Freeware)

[Drahken]

I would recommend using xnview's export function over it's save/save as function (either file->export, or ctrl+alt+s). It tends to give you more options and/or easier access to the options, lets you see a preview of the result, and easily compare results between JPG, TIFF, PNG, GIF, BMP, TGA, PCX, and jpeg2000.

If you use the export function, PNG format, compression level 9, and "sub" filter, that "myfirstfractal.bmp" pic can be reduced to 1.29MB, without using the RIOT plugin, PNGoptimizer, nor any other plugins.

If you use the JPG format, quality=90, and (this is the most important part) subsampling factor 1x1, 1x1, 1x1 (best quality), you can get an image that's only 792KB, yet has little or no visible loss in quality. People think JPG -must- look bad, but it's just because most JPGs were saved favoring size over quality. The subsampling factor is the key. If that is set low, you will get all the well-known JPG problems like washed out reds & the like. If you set it to the highest quality though, you don't get any of that garbage.
Compare this image: http://allspark.net/cypherswipe/MyFirstFractal.jpg to the one Xntriq linked.
For comparison, here's the same pic, at 90% quality, but with the subsampling set at it's lowest: http://allspark.net/cypherswipe/MyFirstFractal-bad.jpg The filesize is only 468KB, but there's a very visible drop in quality. This is probably the JPG result you're accustomed to seeing.

For sharing your images online or elsewhere, I would strongly recommend using the JPG settings I posted above. For thje master copy though, I would recommend using PNG at a low compression level. The difference in size between a low compressed PNG and a high compressed PNG often isn't all that much, but the speed of the compression process can be much slower for high compression. A PNG at compression level 1 will save every bit as quickly as a BMP, be every bit as lossless, but will be a mere fraction of the filesize.
BMPs should really never be used unless your imaging program has no other lossless format available, they're just way too bloated/ineficient.

[artistgrrl]

Thanks everyone for being so prompt and also giving a thorough explanation of things I was either not aware of, or had a very fuzzy awareness of, lol.

Okay, here's another question about my photography. Both my cameras automatically upload all images as JPGS. How about if I tried a batch operation to convert all these JPG master copies to higher quality versions, using the JPG settings you advised? Since they start out as ordinary JPGs, will this work, since they don't start off as BMPs?

Unfortunately my favorite fractals program only converts final images to BMPs, but I bet I could do a batch process of all images in that folder to high quality JPGs.

[XnTriq]

[...] without using the RIOT plugin, PNGoptimizer, nor any other plugins.

PngOptimizer is not a plug-in, but a standalone program with batch processing capability.

Both my cameras automatically upload all images as JPGS. How about if I tried a batch operation to convert all these JPG master copies to higher quality versions, using the JPG settings you advised? Since they start out as ordinary JPGs, will this work, since they don't start off as BMPs?

• About.com » Graphics Software
  • The Pitfalls of JPEG Compression
  • JPEG Myths and Facts

If I compress a JPEG at 70%, then later reopen it and compress it at 90%, the final image will be restored to a quality setting of 90%.

False. The initial save at 70% introduces a permanent loss in quality that can't be restored. Saving again at 90% quality only introduces additional degradation to an image that has already had considerable loss in quality. If you must decompress and recompress a JPEG image, using the exact same quality setting each time seems to introduce little or no degradation to the unedited areas of the image.

[artistgrrl]

Cool! I chose a large BMP fractal image, found XnView's "export" and set it as advised, quality at 90, subsampling factor at best quality. The original file is 4+ MB, the exported version would be minimized to 1 MB.

Now what does DCT Method mean, and the smoothing factor, what does that do? And do I need to muck with Progressive and the Huffman table optimizer right now, or ever?

Umph. Seems my JPGs in the fractals folder would actually become heavier files, we don't want that. Shouldn't be using JPG fractals anyway, I have the "spot files" for some of them and can do them over as BMPs and then convert. That's the plan anyway.

[Drahken]

Smoothing factor does what the name implies, it smoothes the image somewhat. This smoothing isn't enough to be noticable on most images, but may be noticable on something like fractals. A high smoothing factor will reduce filesize but will make the image more lossy/lower visual quality. Since quality is your highest concern with the fractal pics, I would suggest putting it at 0. For other images where fine detail is less important, you may want to go up to 10 to decrease the filesize.
To see the difference for yourself, drag the image in the preview window to a detailed section of the image & try the different settings. You should also hit the + magnifying glass a few times to zoom in so that you can see the results better.

DCT method swaps out speed for size, but leaves quality intact. It doesn't make a huge difference in either size nor compression speed on most images, so it doesn't matter much what setting you choose.

You should have the huffman table option checked for all pics. It decreases the filesize more, without affecting quality. It might add a little time to the compression, but if so it's so little that you can't even measure it.
The progressive option should also be checked for most pics, but will backfire slightly on a few pics. In practice this has the same general effect as the huffman table one, in reduces the size of most pics without affecting quality. Once in a while though, it will actually INcrease the size slightly. This is rare though & doesn't make a major difference, so it's safe to leave checked all the time.
The primary purpose of the progressive option has to do with how the image downloads/displays on a slow connection. Have you ever noticed how some pics will load at perfect quality, from the top to the bottom, while others will load a full pic at low quality & then build up the quality as the pic downloads? Choosing the "progressive" option means that that pic will download at low quality & build up the quality as the pic loads. The reduction in filesize is an unintended (but useful) side effect of this.
Neither of these options will have a huge impact on filesize, but every little bit helps (especially if it doesn't hinder quality).

Seems my JPGs in the fractals folder would actually become heavier files

That's probably because they were previously saved with lower quality settings (for example, the low quality subsampling option is default in most image viewers/editors. In fact, many don't even give you the option of changing it, xnview is one of the few that does.)
As Xntriq said, saving those files as higher quality JPGs would do no good, they would still retain their current data loss but be bigger files. If you can recreate them or have them as BMPs, then you could create new, high quality JPGs for them. The filesize of these new JPGs will still be larger than your current JPGs for them, BUT they will be much higher quality than your current JPGs, making it well worth the tradeoff.





Xntriq:

PngOptimizer is not a plug-in, but a standalone program with batch processing capability.

*shrug* Hard to keep track of which ones are purely stand-alone progs, which ones are both stand-alone & plugins, and which are just plugins. My underlying point remains the same though, that the results can be achieved with xnview alone, and that it's much quicker than most (all?) PNG optimizing programs and plugins, which tend to use brute force & a great deal of processor cycles to shave just a few bytes off the pic.



Speaking of batch processing:
artistgrrl- If you have a lot of BMPs to convert, you can use xnview to batch convert instead of 1 by 1. All the important quality settings are available for plain saving & for batch converting (minus the preview window), they just take an extra step or two to get to.
To batch convert, open xnview, then go tools->batch processing, select your files, choose JPG as the output, then click the options button, and select the settings we already discussed.
You will find a few new options here;
The estimated quality one is irrelevant unless you started out with JPGs.
Rebuild embedded thumbnail is probably also irrelevant unless you started with photos from a camera. You should always have that option marked just in case. (If you don't & your original image had an embedded thumbnail, then sometimes the resulting image will still be bloated because it has a huge thumbnail. In experiments, I've wound up with images where the thumbanil was actuall significantly larger than the final image.)
The 4 "keep [...]" options; If you are working with images from a camera, you'll probably want these checked. If working with images you created from a program, you'll probably want to UNcheck them. All 4 of these are about non-image data. The EXIF and IPTC ones contain data about when the pics were created, what camera settings were used, etc. This info will probably be useful to a dedicated photographer, though it is altogether meaningless to most of us. The ICC profile one has to do with how the colors in your image will be displayed on different computers. Support for this is lacking/incomplete/buggy in most browsers, so it's kinda useless. I'm not certain exactly what the XMP data is.
UNchecking any of these 4 options will remove the respective data from your image PERMANENTLY. It will usually reduce filesize somewhat, but usually not a lot. If you are not certain, you should go ahead and have all 4 of these options CHECKED. this is the safest option.

If you are using xnview's browser mode, you can select all the images you want to convert before going into tools->batch processing, this will avoid having to select the files via the "add files" option in the batch processing window.

[XnTriq]

Again: I'd rather convert the BMP fractals to PNG. You can't go wrong with that. File sizes will shrink considerably, but image detail will be peserved.

The following animation shows the difference between the original and Drahken's MyFirstFractal.jpg at 400% zoom:

• 

The distortions (JPEG compression artifacts) are clearly visible in the yellow and olive areas.

Now what does DCT Method mean, and the smoothing factor, what does that do? And do I need to muck with Progressive and the Huffman table optimizer right now, or ever?

• 

Progressive JPEGs display gradually as they download, so they will appear initially at a very low quality and slowly become clearer until the image is fully downloaded. On a slow dial-up connection, this may give the illusion of a faster download, but usually a progressive JPEG is larger in file size and requires more processing power to decode and display. Also, some software is incapable of displaying progressive JPEGs, most notably, the free Imaging program bundled with many versions of Windows.

The simplest reason is that your images are 'progressive' JPGs.
There are three ways of saving JPGs:
1. Baseline
2. Baseline Optimized (in Photoshop - I'm not sure how it differs from Baseline)
3. Progressive - essentially designed for the dark days before broadband. The image is built in 'layers' so thet users of slow lines would see it appear gradually 'all over' instead of very slowly from top to bottom.
Image editors usually give you a choice of JPG format. I don't know of anything which lumbers you with Progressive, like it or not

Generally, DVD players will not read (3). I don't know about (2), but are happy with (1).

I've many pictures that were compressed as "progressive jpeg" but my pioneer dvd player can't play them, only can play baseline jpeg pictures, so I would like to know if it's possible a loosless jpeg conversion from progressive to baseline with xnview.

<!–––––––––––––––––––––––––––––– // cut here // ––––––––––––––––––––––––––––––>8

My underlying point remains the same though, that the results can be achieved with xnview alone, and that it's much quicker than most (all?) PNG optimizing programs and plugins, which tend to use brute force & a great deal of processor cycles to shave just a few bytes off the pic.

That's the case with other optimizers I've tried over time, but even on my decade-old 1GHz Pentium III PC Nilsson's PngOptimizer processed MyFirstFractal.bmp in the blink of an eye, while choosing the appropriate filter automatically.

• 

[artistgrrl]

If you have a lot of BMPs to convert, you can use xnview to batch convert instead of 1 by 1.

** Great, I was hoping for that, since I have a bajillion photos...

The estimated quality one is irrelevant unless you started out with JPGs.

*** Not quite sure what that means? I quote myself = "Seems my JPGs in the fractals folder would actually become heavier files..."

And then yourself =

That's probably because they were previously saved with lower quality settings (for example, the low quality subsampling option is default in most image viewers/editors. In fact, many don't even give you the option of changing it, xnview is one of the few that does.)

** True, I have two versions of Paint Shop Pro and I would have thought version 10 would have had subsampling options that we could control. I looked all around for it but it isn't there, bhah.

**Also-

As Xntriq said, saving those files as higher quality JPGs would do no good, they would still retain their current data loss but be bigger files.

** I've been reading the About.com info on JPGs and a lot of what they say I already knew or suspected.

If you can recreate them or have them as BMPs, then you could create new, high quality JPGs for them.

** No way to recreate the photos, I've been doing digital photography for 8 or 9 years and currently I am focusing on just the shots taken this past year alone. But could they be batch processed into BMPs or would that do any good?

** One thing I can do is check my camera settings to make sure they're set for the highest quality shots I can get.

[Drahken]

** No way to recreate the photos,

I didn't have the photos in mind when I said that. You were talking about the JPGs in your fractals folder, indicating that they were JPGs of fractals, which you had made previously. Additionally, you talked about having the "spot files" (which I assume are some sort of templates to make fractals from) and remaking them as BMPs. This is what I was talking about in regards to recreating images. The fractals, not the photos.


As for the estimated quality thing: If you start out with a BMP or PNG or other format image (ie, if you're starting with a fractal you created) & then convert it to a JPG, the estimated quality option has absolutely no effect.
However, if you convert from JPG to JPG (which would be pointless, unless you want to resize, crop, or perform some other transformation on them), the estimated quality option attempts to estimate the quality used in the original JPG and use the same quality for the new one. Since it isn't completely accurate though (there's no way to accurately know what compression settings were used in the original pic unless you created it yourself & remember what settings you used), the only purpose it really serves is to keep the filesize fairly low if you try to use a quality setting that's well above the original setting.
Essentially; If the original pic was saved at 70% quality and you re-saved it at 90%, the actual visual quality would remain the same, but the filesize would be much larger. However, if you had the estimated quality option checked and re-saved the same pic at 90%, this time it would wind up saving it at about 75%~80% (that seems to be about as accurate as it can guess), resulting in a file smaller than the 90% alone would have been, though still larger than 70%.
The estimated quality option does not go higher than what you chose for the slider though. So if it detects the original as 75% and you set the slider to 60%, the pic will get saved at 60%.

could they be batch processed into BMPs or would that do any good?

1) Never waste time converting anything to BMP. It's a very outdated & almost 100% useless format. As I said before, if you want perfect quality, go for PNG. At low compression it's every bit as fast & as lossless as BMP, but several times smaller.
2) Converting a JPG to any other format will not improve it. The loss it has already experienced is permanent, there is no way to undo it.
If you plan to do a lot of editting or converting to the image over time, then making a lossless master copy would be a good idea. While it won't remove the existing data loss, it will prevent any additional loss. In this respect, converting existing JPGs to a lossless format like PNG is better than converting them to a higher quality JPG, because recompressing the JPG might incur additional loss.


re "progressive": As Xntriq pointed out, there are sometimes compatability problems with progressive JPG images. However, this generally only occurs when they are viewed on either very old or very cheapass DVD players & digital picture frames.
This begs the question: What exactly do you intend to do with these images? Just view them on your computer? Put them online? Put them on a photo disc to view on a DVD player? ...?
This question also affects your format choices to a certain degree. JPG and PNG are the best choices for compatability related reasons. However, there are other lossless formats besides BMP and PNG (both BMP and PNG are always lossless, while JPG is lossy. A lossless format will always give you the best quality, because it will always be perfect quality. However, different lossless formats can achieve different sizes, especially on different types of images. PNG achieves the best sizes on graphic type images, ones with large areas of solid color & sharp edges. Other formats though beat PNG on photographic type images. However, these formats are not as universally compatible as PNG.
Meanwhile, JPG (not counting "lossless JPG", which is a related but different format) will always degrade the image quality to some degree, but will give a great size & the quality losses can usually be kept below noticable levels).

[artistgrrl]

The fractals, not the photos.

** Ahh. Yes, some of them will be redone, that is possible. And, a "spot file" is a parameter file that can only be opened in that particular fractals program that I use. I have certain other ones, and each program has its own special file extension.

If you plan to do a lot of editting or converting to the image over time, then making a lossless master copy would be a good idea. While it won't remove the existing data loss, it will prevent any additional loss. In this respect, converting existing JPGs to a lossless format like PNG is better than converting them to a higher quality JPG, because recompressing the JPG might incur additional loss.

** As mentioned, I have something like 8 yrs' worth of images and they are all auto-saved as JPGs. But, as I work with those I'm focusing on at present, they will have a special editing file created for each one, which gets saved back to a JPG for online viewing.

** BTW, I investigated my cameras and neither of them has a quality choice option (my older digital camera did, though!) but it does allow for really huge "high resolution" images (up to 14 MP). I realize images that large would still look good downsized, but who needs an image that large unless you're using it for a wall mural?

. . . compatability problems with progressive JPG images. However, this generally only occurs when they are viewed on either very old or very cheapass DVD players . . .

** Oops! I hope my not-so-new DVD players won't give me trouble! The oldest is, maybe 7 yrs?

This begs the question: What exactly do you intend to do with these images? Just view them on your computer? Put them online? Put them on a photo disc to view on a DVD player? ...?

** Actually, all three. Most of them, the best ones, do go online, as I have two webblogs for that purpose. Those are the ones that most need to be the highest quality I can achieve. Copies of the best photos (as well as some that didn't quite make the cut but are still acceptable) will go on photo disks for family viewing.

** Well, I just did my first batch processing (to JPG with the correct settings) for the most recent BMP fractals. But they are still mixed in with the other lower-quality images and original BMPs, kind of hard to see which is which in there. Is there a way to export processed images into a new folder or subfolder when they're done, so that they can be got at quickly?

[Drahken]

For putting the pics online, high quality JPGs will probably be your best option. They can retain the vast majority of the quality, but with a significant drop in filesize. For the best quality, set the smoothing factor to 0. You can bump the quality slider up to 95% if you want, but I wouldn't go higher than that. Beyond that, you get massive size increases with each percentage, but little or no quality increase.
All browsers can handle progressive JPGs with ease, so there's no issue there.
If you want the absolute best quality though, use PNGs with level 9 compression & the "sub" filter. The resulting images will be about twice the filesize of the comparable JPGs, but still only a fraction as large as the BMPs. In exchange for the increased size, they will have perfect, 100% lossless quality.
Also, with PNGs you should leave the "interlaced" option UNchecked. It does the same thing as progressive JPGs in the sense that the image will load at low quality & build up, but unlike progressive JPGs, interlaced PNGs will always be larger filesize than standard ones. (Unlike progressive JPGs though, there are no compatability concerns with interlaced PNGs. The PNG format was fully developed before it was released, so it has very few compatability issues. The JPG format in contrast just sort of grew up over time. It wasn't even an official format until pretty recently, just a de facto standard.)


With older DVD players, you never know for sure if they can handle progressive JPGs until you try. Either make a disc with some progressives on it & try it in all your players, or just assume they can't and keep the progressive option UNchecked.
I do not know whether or not DVD players can handle PNGs at all. Again, the only way to know for sure is to try it & see.

re batch processing: Right above where you select the output format is a spot to select the output folder. You can create a subfolder & then have xnview dump the converted images in there. Something like c:\fractals\jpgs or whatever. Make sure that the "use original" option is UNchecked though.

[JohnFredC]

This is a great thread and loaded with useful info. With a bit of editing and consolidation, the material presented herein would make a good addition to the help resources.

[Drahken]

I think the basics of this is already in one or more of my existing FAQs, like the file format one, some of them just need updated with more recent info (because many of these JPG settings for example weren't available in xnview at the time, like the subsampling one).

[artistgrrl]

You can bump the quality slider up to 95% if you want, but I wouldn't go higher than that.

** I wondered about that too. I've been leaving it on 90 percent. I have a good photo-stitch program where the default is, like, 80 percent. And someone told me that the difference between 80 and 100 percent is so minimal that it's irrelevant. I've tried 100 percent in the stitch program but I see no quality change and don't even see that the filesize has any changes.

. . . interlaced PNGs will always be larger filesize than standard ones.

** That's something else I've seen around, but never knew what it meant. See, I'm learning tons here!

. . . I do not know whether or not DVD players can handle PNGs at all.

** I never gave that a passing thought till now, all during the years I was blissfully unaware of the differences in file formats, various quality probs, and compatibility issues. For many years, in my humble opinion a JPG was a JPG was a JPG, lol!

. . . Right above where you select the output format is a spot to select the output folder.

** Yes, just after I asked about that, I did notice it, thanks... and now I'll know what to do with it.

** I've been seeing more "progressive" JPGs online these days, more than even a year or two ago. Up until now I was one of those unfortunate folk stuck on slow rural dial-up. At present I have a means of receiving high speed internet for the first time ever (although I am still keeping my dialup for backup "just in case"). But on dialup I was very familiar with the blocky images that gradually become clearer. I also have that option on my older version of Paint Shop Pro, to make your final image progressive if you wish. Something else I never paid much mind to, not knowing what it was. I always preferred seeing an online image download from top to bottom over a white area, but I guess that is b/c I was used to that (it seemed comparatively faster than progression). On high speed internet, though, I can see that "progressive" only takes a couple of seconds before the image is clear. However, in working with my photos, I will avoid that option if it might give trouble on my DVD player...and, true, I don't know yet whether it can even show PNGs.

This is a great thread and loaded with useful info.

** Thanks, glad to be of help, LOL. And here I was beginning to feel a bit silly asking so many N00B questions. But how ya gonna learn without asking a lot of questions? Sometimes it seems any FAQ section is "above my head" anyway, in some respects...sometimes I just need more detail.