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As a general rule of thumb when is it appropriate to make a gif interlaced, a png interlaced and a jpeg progressive?
Especially when publishing the image on the web.
JPEG: YES — use progressive scan. It makes files smaller (each pass gets its own Huffman table), and partial rendering looks quite good.
GIF: NO — it's unlikely to make the file smaller, partial rendering is poor, and it's pointless for animGIFs. It's best not to use GIF at all (yes, even for anims).
PNG: NO — it hurts compression (as data from each pass is statistically quite different). If the image is large, use high-quality JPEG or lossy PNG if possible, as these may load quicker than a pixelated preview of a large lossless PNG.
ImageOptim will automatically change progressive/interlaced formats when it makes files smaller.
Disclaimers for nitpickers:
In case of small and medium-sized images the progressive preview of each image is not going to be visible long enough for the user to appreciate it. Some browsers don't even bother rendering anything until the whole file is downloaded, so it's better to focus on saving bandwidth to get the whole page loaded ASAP.
Non-progressive JPEG is a bit more efficient when the files are tiny (small thumbnails), but then the savings are tiny, too.
iOS Safari has a higher maximum allowed image size for baseline JPEG than progressive, but the right solution there is to serve images at sizes reasonable for mobile in the first place.
My general rule of thumb: don't ever use interlacing. Interlaced formats typically occupy more space, have (slightly) more complexity and less support in decoders, and the alleged advantages for the user experience are at least debatable. Some arguments for PNG, and in general.
Some people like interlaced or "progressive" images, which load
gradually. The theory behind these formats is that the user can at
least look at a fuzzy full-size proxy for the image while all the bits
are loading. In practice, the user is forced to look at a fuzzy
full-size proxy for the image while all the bits are loading. Is it
done? Well, it looks kind of fuzzy. Oh wait, the top of the image
seems to be getting a little more detail. Maybe it is done now. It is
still kind of fuzzy, though. Maybe the photographer wasn't using a
tripod. Oh wait, it seems to be clearing up now ...
Interlaced images are slightly less efficient, but show up after shorter delay on the client side when transported over the network. IMHO they should be used when the expected download time for the image is long enough to be perceived by the user (say, above 1 second). The difference in file size is really quite small, so it's better to be too-cautious and use interlacing too much rather than too little.
In common broadband internet as of 2012, I'd just use it for every image > 100kb.
These points must be useful.
Interlacing (more generally, progressive display) is a method of displaying images on a monitor.
When to use it? Your decision should be base on these factors:
•> Non-interlaced images are smaller than interlaced images.
•> Interlaced images cause less flickering than non-interlaced ones
•> Interlaced images are much more easily view-able.
The interlace lets you see the picture before all the data has been transmitted (makes them appear faster and better-looking) and gives you the "feeling" that it is being downloaded faster.
TIP: Interlacing is not recommended for small images but is a must if
the viewer uses a slow connection
This is just a copy from Y answers i thought could help to understand.
Original answer could be find at: https://answers.yahoo.com/question/index?qid=20090211121956AAz7Xz8
Just to throw my twopenneth into the argument: Interlacing was introduced years ago when internet speeds were slow, the idea being that the image would present itself in a gradually more defined manner, still giving an overall look and feel to an image without having to wait for the entire thing to load.
Interlacing, today, is basically unnecessary and should be used based on the overall size of the image being transferred.
Progressive scans on JPEG images images do provide a more refined image while attempting to reduce the overall file size (i.e. is an actual compression mode rather than a streaming method for the bits making up the image).
PNGs use a more complex algorithm than GIF.
There is an interesting related post on webmasters
https://webmasters.stackexchange.com/questions/574/progressive-jpeg-why-do-many-web-sites-avoid-rendering-jpegs-that-way-pros
Untimately it depends on how they are going to be used.
The post suggests that there is limited - genuine - support for progressive images. And sometimes they may cause issues with plugins which don't support the progressive format.
Hope that helps.
Consider an application handling uploading of potentially very large PNG files.
All uploaded files must be stored to disk for later retrieval. However, the PNG files can be up to 30 MB in size, but disk storage limitations gives a maximum per file size of 1 MB.
The problem is to take an input PNG of file size up to 30 MB and produce an output PNG of file size below 1 MB.
This operation will obviously be lossy - and reduction in image quality, colors, etc is not a problem. However, one thing that must not be changed is the image dimension. Hence, an input file of dimension 800x600 must produce an output file of dimension 800x600.
The above requirements outlined above are strict and cannot be changed.
Using ImageMagick (or some other open source tool) how would you go about reducing the file size of input PNG-files of size ~30 MB to a maximum of 1 MB per file, without changing image dimensions?
PNG is not a lossy image format, so you would likely need to convert the image into another format-- most likely JPEG. JPEG has a settable "quality" factor-- you could simply keep reducing the quality factor until you got an image that was small enough. All of this can be done without changing the image resolution.
Obviously, depending on the image, the loss of visual quality may be substantial. JPEG does best for "true life" images, such as pictures from cameras. It does not do as well for logos, screen shots, or other images with "sharp" transitions from light to dark. (PNG, on the other hand, has the opposite behavior-- it's best for logos, etc.)
However, at 800x600, it likely will be very easy to get a JPEG down under 1MB. (I would be very surprised to see a 30MB file at those smallish dimensions.) In fact, even uncompressed, the image would only be around 1.4MB:
800 pixels * 600 pixels * 3 Bytes / color = 1,440,000 Bytes = 1.4MB
Therefore, you only need a 1.4:1 compression ratio to get the image down to 1MB. Depending on the type of image, the PNG compression may very well provide that level of compression. If not, JPEG almost certainly could-- JPEG compression ratios on the order of 10:1 are not uncommon. Again, the quality / size of the output will depend on the type of image.
Finally, while I have not used ImageMagick in a little while, I'm almost certain there are options to re-compress an image using a specific quality factor. Read through the docs, and start experimenting!
EDIT: Looks like it should, indeed, be pretty easy with ImageMagick. From the docs:
$magick> convert input.png -quality 75 output.jpg
Just keep playing with the quality value until you get a suitable output.
Your example is troublesome because a 30MB image at 800x600 resolution is storing 500 bits per pixel. Clearly wildly unrealistic. Please give us real numbers.
Meanwhile, the "cheap and cheerful" approach I would try would be as follows: scale the image down by a factor of 6, then scale it back up by a factor of 6, then run it through PNG compression. If you get lucky, you'll reduce image size by a factor of 36. If you get unlucky the savings will be more like 6.
pngtopng big.png | pnmscale -reduce 6 | pnmscale 6 | pnmtopng > big.png
If that's not enough you can toss a ppmquant in the middle (on the small image) to reduce the number of colors. (The examples are netpbm/pbmplus, which I have always found easier to understand than ImageMagick.)
To know whether such a solution is reasonable, we have to know the true numbers of your problem.
Also, if you are really going to throw away the information permanently, you are almost certainly better off using JPEG compression, which is designed to lose information reasonably gracefully. Is there some reason JPEG is not appropriate for your application?
Since the size of an image file is directly related to the image dimensions and the number of colours, you seem to have only one choice: reduce the number of colours.
And ~30MB down to 1MB is a very large reduction.
It would be difficult to achieve this ratio with a conversion to monochrome.
It depends a lot on what you want at the end, I often like to reduce the number of colors while perserving the size. In many many cases the reduced colors does not matter. Here is an example of reducing the colors to 254.
convert -colors 254 in.png out.png
You can try the pngquant utility. It is very simple to install and to use. And it can compress your PNGs a lot without visible quality loss.
Once you install it try something like this:
pngquant yourfile.png
pngquant --quality=0-70 yourfile.png
For my demo image (generated by imagemagick) the first command reduces 350KB to 110KB, and the second one reduces it to 65KB.
Step 1: Decrease the image to 1/16 of its original size.
Step 2: Decrease the amount of colors.
Step 3: Increase the size of the image back to its original size.
I know you want to preserve the pixel size, but can you reduce the pixel size and adjust the DPI stored with the image so that the display size is preserved? It depends on what client you'll be using to view the images, but most should observe it. If you are using the images on the web, then you can just set the pixel size of the <img> tag.
It depends on they type of image, is it a real life picture or computer generated image,
for real life images png will do very little it might even not compress at all, use jpg for those images, it the image has a limited number of different colors (it can have a 24 bit image depth but the number of unique images will be low) png can compress quite nicely.
png is basicly an implementation of zip for images so if a lot of pixels are the same you can have a rather nice compression ratio, if you need lossless compression don't do resizing.
use optipng it reduce size without loss
http://optipng.sourceforge.net/
Try ImageOptim https://imageoptim.com/mac it is free and open source
If you want to modify the image size in ubuntu, you can try "gimp".
I have tried couple of image editing apps in ubuntu and this seemed to be the best among them.
Installation:
Open terminal
Type: sudo apt install gimp-plugin-registry
Give admin password. You'll need net connection for this.
Once installed, open the image with GIMP image editor. Then go to: File > Export as > Click on 'Export' button
You will get a small window, where check box on "Show preview in image window". Once you check this option, you will get to see the current size of the file along with Quality level.
Adjust the quality level to increase/decrease the file size.
Once adjusting is done, click on 'Export' button finally to save the file.
Right click on the image. Select open with paint. Click on resize. Click on pixel and change the horizontal to 250 or 200.
That's the only thing. It is the fastest way for those who are using Windows XP or Windows 7.
I'm creating barcodes on the fly, and embedding them in web pages. What format should I use? I'm wavering between JPG and PNG, and I don't really understand the advantages of both. Size matters in this, as does readability (better a clear barcode than a blurry one). Is there another format that would be better yet?
PNG, or even GIF. Jpeg is right out, because it's designed for the smooth gradients of photographs, not the sharp edges of bar codes. Draw a simple Bar code by hand in MS Paint, save it, and then reload it, you'll see all kinds of compression artifacts.
Definitely PNG. It's much better at storing vector graphics, such as bar codes (as opposed to photos).
Wikipedia has a nice comparison of JPG vs. PNG.
PNG should be better than JPG (JPG is lossy). GIF might be even better since the image is going to be monochrome (but check it in your case).
PNG is the better option between PNG and JPG. The main issue here is of compression - there are two forms of compression techniques in images, lossy and lossless. Lossy compression algorithms (such as the one used by JPG files) "lose" information during the compression->decompression cycle. Because of this, there will be artifacts in your image. PNG, on the other hand, uses lossless compression, so the displayed image will be exactly the same as the original, uncompressed imagery prior to the initial saving.
In the case of barcodes, the exact pixel-by-pixel placement of black/white is very important (that's the entire point), so using a lossy compression routine like JPG could be very bad. If you're using a 2D barcode, it will be even worse, and your scanner may have a very difficult time reading the barcode accurately. PNG will completely eliminate this problem.
I have used .gif and .png successfully. My answer (and other answers, to be fair) to this question has more detail.
PNG all the way. It will not only avoid the compression artifacts you'll get with JPG, but will almost certainly yield better compression as well. JPG is very badly suited to images with sharp edges.
I have a very large background image (about 940x940 pixels) and I'm wondering if anyone has tips for compressing a file this large further than Photoshop can handle? The best compression without serious loss of quality from Photoshop is PNG 8 (250 KB); does anyone know of a way to compress an image down further than this (maybe compress a PNG after it's been saved)?
I don't normally deal with optimizing images this large, so I was hoping someone would have some pointers.
It will first depend on what kind of image you are trying to compress. The two basic categories are:
Picture
Illustration
For pictures (such as photographs), a lossy compression format like JPEG will be best, as it will remove details that aren't easily noticed by human visual perception. This will allow very high compression rates for the quality. The downside is that excessive compression will result in very noticeable compression artifacts.
For illustrations that contain large areas of the same color, using a lossless compression format like PNG or GIF will be the best approach. Although not technically correct, you can think of PNG and GIF will compress repetitions the same color very well, similar to run-length encoding (RLE).
Now, as you've mentioned PNG specifically, I'll go into that discussion from my experience of using PNGs.
First, compressing a PNG further is not a viable option, as it's not possible to compress data that has already been compressed. This is true with any data compression; removing the entropy from the source data (basically, repeating patterns which can be represented in more compact ways) leads to the decrease in the amount of space needed to store the information. PNG already employs methods to efficiently compress images in a lossless fashion.
That said, there is at least one possible way to drop the size of a PNG further: by reducing the number of colors stored in the image. By using "indexed colors" (basically embedding a custom palette in the image itself), you may be able to reduce the size of the file. However, if the image has many colors to begin with (such as having color gradients or a photographic image) then you may not be able to reduce the number of colors used in a image without perceptible loss of quality.
Basically it will come down to some trial-and-error to see if the changes to the image will cause any change in image quailty and file size.
The comment by Paul Fisher reminded me that I also probably wouldn't recommend using GIF either. Paul points out that PNG compresses static line art better than GIF for nearly every situation.
I'd also point out that GIF only supports 8-bit images, so if an image has more than 256 colors, you'll have to reduce the colors used.
Also, Kent Fredric's comment about reducing the color depth has, in some situtations, caused a increase in file size. Although this is speculation, it may be possible that dithering is causing the image to become less compressible (as dithering introduces pixels with different color to simulate a certain other color, kind of like mixing pigment of different color paint to end up with another color) by introducing more entropy into the image.
Have a look at http://www.irfanview.com/, is an oldy but a goody.
Have found this is able to do multipass png compression pretty well, and does batch processing way faster than PS.
There is also PNGOUT available here http://advsys.net/ken/utils.htm, which is apparently very good.
Heres a point the other posters may not have noticed that I found out experimentally:
On some installations, the default behaviour is to save a full copy of the images colour profile along with the image.
That is, the device calibration map, usually SRGB or something similar, that tells using agents how to best map the colour to real world-colours instead of device independant ones.
This image profile is however quite large, and can make some of the files you would expect to be very small to be very large, for instance, a 1px by 1px image consuming a massive 25kb. Even a pure BMP format ( uncompressed ) can represent 1 pixel in less.
This profile is generally not needed for the web, so, when saving your photoshop images, make sure to export them without this profile, and you'll notice a marked size improvement.
You can strip this data using another tool such as gimp, but it can be a little time consuming if there are many files.
pngcrush can further compress PNG files without any data loss, it applies different combinations of the encoding and compression options to see which one works best.
If the image is photographic in nature, JPEG will compress it far better than PNG8 for the same loss in quality.
Smush.It claims to go "beyond the limitations of Photoshop". And it's free and web-based.
It depends a lot on the type of image. If it has a lot of solid colors and patterns, then PNG or GIF are probably your best bet. But if it's a photo-realistic image then JPG will be better - and you can crank down the quality of JPG to the point where you get the compression / quality tradeoff you're looking for (Photoshop is very good at showing you a preview of the final image as you adjust the quality).
The "compress a PNG after it's been saved" part looks like a deep misunderstanding to me. You cannot magically compress beyond a certain point without information loss.
First point to consider is whether the resolution has to be this big. Reducing the resolution by 10% in both directions reduces the file size by 19%.
Next, try several different compression algorithms with different grades of compression versus information/quality loss. If the image is sketchy, you might get away with quite rigorous JPEG compression.
I would tile it, Unless you are absolutely sure that you audience has bandwidth.
next is jpeg2k.
To get more out of a JPEG file you can use the 'Modified Quality Setting' of the "Save as Web" dialog.
Create a mask/selection that contains white where you want to keep the most detail, eq around Text. You can use Quick-Mask to draw the mask with a brush. It helps to Feather the selection, this results in a nice white to black transition in the next step.
save this mask/selection as a channel and give the channel a name
Use File->Save as Web
Select JPEG as file format
Next to the Quality box there is a small button with a circle on it. Click that. Select the saved channel in step 2 and play with the quality setting for the white and black part of the channel content.
http://www.jpegmini.com is a new service that creates standard jpgs with an impressively small filesize. I've had good success with it.
For best quality single images, I highly recommend RIOT. You can see the original image, aside from the changed one.
The tool is free and really worth trying out.
JPEG2000 gives compression ratios on photographic quality images that are significantly higher than JPEG (or PNG). Also, JPEG2000 has both "lossy" and "lossless" compression options that can be tuned quite nicely to your individual needs.
I've always had great luck with jpeg. Make sure to configure photoshop to not automatically save thumbnails in jpegs. In my experience I get the greatest bang/buck ratio by using 3 pass progressive compression, though baseline optimized works pretty well. Choose very low quality levels (e.g. 2 or 3) and experiment until you've found a good trade off.
PNG images are already compressed internally, in a manner that doesn't benefit from more compression much (and may actually expand if you try to compress it).
You can:
Reduce the resolution from 940x940 to something smaller like 470x470.
Reduce the color depth
Compress using a lossy compression tool like JPEG
edit: Of course 250KB is large for a web background. You might also want to rethink the graphic design that requires this.
Caesium is the best tool i have ever seen.
As probably many people around here I read a few webcomics. Drowtales is my favorite, but that's besides the point.
For a long time a thought has been nagging me at the back of my head: webcomics are drawn pictures. They are not photographs. There should be a lot of redundancy (less colors, more flat colored areas, etc.) and thus they should be easily compressible at quite high rates while still maintaining lossless quality. Still it seems that the best tool to compress them is the same old lossy JPEG.
How so? Are there not better things invented? I'm not an expert in data compression, so my own meager attempts at finding some better algorithm have been fruitless. Best I could find was Pngcrush, but it still is way behind JPEG in terms of compression.
I would like to hear an expert opinion on this. Is this idea of mine foolish and doomed to failure? Or is there perhaps some way that people have found or that I could look into?
This, of course, comes from the selfish desire to decrease load times. :)
Added: Some people seem to miss the point, so I'll clarify:
Webcomic images should have a lot of redundancy in them so they should be easily compressible. Is it not possible to somehow compress them so that they would be both lossless AND smaller than JPEG? Or at the very least compress them better than JPEG while still retaining the quality.
Since they would be for web the specialized compressor should still probably emit PNG or JPEG - just compressed with a modified algorithm for better results.
No question, it's a balancing act between appearance and performance. Barring a custom compression algorithm specifically for comics, I think the best you can do is experiment with JPEG compression levels until you get one that's a reasonable size, but still looks good for the particular comic.
From lbrandy.com
The problem with comics is that a lot of graduated colouring is used. A common technique when colouring a comic on computer using Photoshop, for example, is to start by blocking out areas in solid colour as you mentioned. However, these solid areas are then refined using various techniques, from hand touching using airbrush tools to overlaying graduated fills, dodging and burning tools, etc.
The result is an image which is more like a natural image - which is what comic artists are striving for of course - and thus it compresses better with a lossy algorithm such as that used by JPEG.
A completely different approach would be to render the comic images using a vector format like SVG. That would capture the essence of the drawing (fill here, arc here, line here, etc) without having to try to raster-compress the resulting images.
Your assumptions aren't borne out by my data. My favorite webcomic is already distributed as PNG. Converting a 167K PNG file to JPEG using the default compression quality yields a 199K JPEG file. Break-even is somewhere between -quality 60 and -quality 65, which is quite a low quality for a JPEG. So, Questionable Content is already compressed lossless and smaller than JPEG.
A few things I've picked up on doing images for web use -
Use jpegtran -optimise on JPEGs - it recompresses them losslessly and can shave a good few percent off poorly compressed images.
I run PNG files through pngnq (make them 8 bit) and then optipng -i0 (recompress and remove any interlacing). I know you said you don't like lossy, but pngnq does an amazingly good job of converting images to a palette - best thing to do is try it yourself and see if the output is good enough.
Under certain circumstances, JPEG images will be larger than PNG images.
For example, in cases where there is a very simple image, PNG may end up compressing the image better and giving better image quality.
Here's an example with some Java code:
public static void main(String[] args)
{
BufferedImage img = new BufferedImage(
256,
256,
BufferedImage.TYPE_INT_RGB
);
Graphics g = img.getGraphics();
g.setColor(Color.white);
g.fillRect(0, 0, 256, 256);
g.setColor(Color.black);
g.drawLine(0, 0, 255, 255);
g.drawLine(255, 0, 0, 255);
try
{
ImageIO.write(img, "jpg", new File("output.jpg"));
ImageIO.write(img, "png", new File("output.png"));
}
catch (IOException e) {} // Don't usually ignore exceptions!
g.dispose();
}
The above code produces an image with the dimensions of 256 x 256 pixels, and draws two intersecting diagonal lines in the form on an "X".
The 256 x 256 image was used to keep the image size to an multiple of 8, as JPEG compression performs a 2D DCT transform on 8 x 8 pixel sections of the image. By keeping the image size and location of the line to align within the 8 x 8 pixel section, it will reduce the amount of compression artifacts and improve the quality of the image.
(Choosing 256 x 256 was empirical -- I at first used 100 x 100 and noticed that the JPEG image was horrible, so I tried 64 x 64 and it looked better, so I made it larger to simulate a more realistic image size.)
After drawing the image, the program generate a JPEG file and a PNG file. (The Java ImageIO library uses the default compression ratio of 0.75f for the compression quality of the JPEG.)
Results:
output.png : 1,308 bytes
output.jpg : 3,049 bytes
Taking a look at the image itself, the JPEG has a little bit of artifacting, but it wasn't very noticeable until I zoomed in with an image editor. Of course, the PNG image is lossless, so it was an exact representation of the original.
To conclude, whether an image is smaller with PNG or JPEG is really up to the source -- there are cases where JPEG can be larger than a PNG and yet the PNG can be better quality. Of course, in practice, generally PNG will be larger than JPEG for a given image.
You may want to cut down on how many colours you are encoding in your image. Try saving your comic with only 256 colours and watch the size decrease a lot. Depending on your specific drawing style, that me be enough.
I've drawn a number of large hand-illustrated circuit diagrams which I scan in as grayscale for use in computerized documents; LZW-compressed TIFF always wins hand over JPEG, both in viewable quality and file size, I think because TIFF can take advantages of RLE encoding for whitespace. I'm not sure whether PNG can do this too, or whether RLE can be extended for multicolor images & not just black/white.
edit: I just tried one of my grayscale hand drawings; TIFF can beat PNG by about 2:1 (43K vs. 83K using ImageMagick convert to go from original TIFF -> PNG -> TIFF again to double-check that ImageMagick is producing both file formats and ensure that my original program didn't do a bad job producing the TIFF) but only because TIFF uses 8bits/pixel (grayscale) and PNG uses 24bits/pixel (RGB).
edit 2: never mind, I just was able to use pngcrush -c 0 to ensure the image is grayscale. PNGcrush got the RGB version down to 67K and the grayscale down to 34K. Nice!
edit 3: Just a point of procedure: It seems to me that it would make a heck of a lot more sense to pick a number of different images of this type to choose as standard benchmarks, and just try different techniques across the benchmark set, rather than just a bunch of stack-overfloids pontificating. This seems like a problem that needs a well-tested empirical solution.
No matter how great a lossless compression is, a loss compression will always be better, because it just has fewer limitations.
Imagine that one day they invent some lossless compression better than jpeg for comics, obviously the next day someone will modify it to compress more, even, and probably, if it means that some info is lost.
Between anti-aliasing and gradients, there are probably more colors in the image than you think.
Drawn vs. not drawn, web comics vs. any other type of image... that's not relevant. The specifics of how web comics are drawn or the colors are laid out or whatever is something you're perceiving as different. But you can bet that decades of graphics research and development have that fully taken into account, and the people that do graphics optimizations for a living have pushed the envelope.
If there was a better compression algorithm than JPEG, GIF, PNG, etc. then don't you think it would be in wide-spread use? If you're looking for fairly recent breakthroughs then I think you're probably wasting your time, as 1) you'd have to expend quite a bit of effort to make your front-end compression compatible with whatever viewer people use (like browsers) and 2) if it had significant gains from current formats then it would become wide-spread fairly quickly.
If I'm getting down-voted I must not have explained myself very well.
Thinking that web comics are in some special domain because they're hand-drawn or have lots of color repetition is a bit silly. Finding large blocks of the same color is one of the absolute basics of image compression.
Get yourself a good graphics program, and using your specific image, see which of its export formats yields the smallest image size while retaining the quality you desire. It is going to be different for different images.
For pen-and-inkish images, the compression scheme in GIF can work wonders.
JPEG compression is ill-suited to that kind of image.
As someone who has done a lot of colouring work for cartoons, as well as photo-manipulation work I can safely say that there is often a lot going on inside the average web-comic when compared to a normal photo.
Assuming that the image is done in Photoshop or Painter (usually from a Tablet) there are often a number of filters or layers at work in the average web-comic. Shading, reflection, opacity, background images and far more come into the equation and with many of these being straight from filters or layer overlays there are often many colours in place.
A lot of the time you have to think of your audience. It is really worth optimising your images if you get 20 visitors a day? I'd probably argue that it is completely down to the size and content of your web-comic. If you can get away with PNG then I'd stick with it. More often than not in web-comics there is little going on to warrant using JPG.
I use OPTIPNG to get the best filter (with a sane level) and then I run ADVDEF -4 -z
http://advancemame.sourceforge.net/comp-readme.html (Not Advpng because Advpng removes the filters) to optimize the deflate.
Also you can try pngout http://www.advsys.net/ken/utils.htm
Has a plugin for Irfanview.
It uses the same deflate implementation of Kzip, which is usually even better than 7-zip but much slower.
EDIT:
okcancel20031003.gif What's your favorite "programmer" cartoon? 256 colors 147KB
PNG (Paint) 126KB
PNG (Irfanview) 120 KB
PNG (Irfanview) +
Optipng -o5 120KB (525 bytes smaller) 9s
Optipng + ADVDEF 114 KB 9s+0.9s
PngOut 114 KB 6s
BMP 273 KB
BMP +
7z (LZMA -fb 273) 107 KB
RAR (Best) 116 KB
BMF -S 90 KB 0.3s
Paq8o10t -4 79 KB 35s
I think the missing piece of information here is Image Compression is Tied to the Format. It's certainly possible that someone could come up with a compression algorithm that was/is well suited for the kind of images that web cartoonists create. However, once you took the new uber-comic-image format and emitted a PNG, JPG or GIF, the color information would be subject to the rules of the PNG, JPG or GIF compression mechanism and you'd lose all the benefit of your new image format.
Here's another way to think about it.
Save a photo as a low quality JPEG
Note the file size
Take that low quality jpeg and save-as a 24/32 bit PNG
Note the larger file size
The same thing would happen to this mythical uber-comic-image format.
The alternative would be getting the major browser vendors to support uber-comic-image nativity. I'll leave the reasons behind that not working as an exercise to the viewer.