Graphic File Size and Quality

[AliTree]

i understand the reason for the rules, but i don't really understand why the amount of kb is so small. i basically can't use any quality colored picture of myself because it's too big. bleh.

[Jezebel]

i understand the reason for the rules, but i don't really understand why the amount of kb is so small. i basically can't use any quality colored picture of myself because it's too big. bleh.

It's because INTJf has limited bandwidth and right now we host everything on-site. Increasing the avatar kb any substantial amount would cost money, otherwise I would gladly raise the limit. Have you read this thread (http://intjforum.com/showthread.php?t=7915)? If you don't have Photoshop or have any other problems, I can get the color images to the appropriate kb with minimal quality loss.

[HackerX]

It's because INTJf has limited bandwidth and right now we host everything on-site. Increasing the avatar kb any substantial amount would cost money, otherwise I would gladly raise the limit. Have you read this thread (http://intjforum.com/showthread.php?t=7915)? If you don't have Photoshop or have any other problems, I can get the color images to the appropriate kb with minimal quality loss.

I really have no idea how somebody could hit the kb limit. Given the size of the image, the 19.2kb? (Guessing from memory) is huge for a jpeg.

[Jezebel]

I really have no idea how somebody could hit the kb limit. Given the size of the image, the 19.2kb? (Guessing from memory) is huge for a jpeg.
Nah, using the standard save feature in Photoshop often gets jpegs around two to three times over our requirements. I can't save them under 19kb without a lot of ugly compression artifacts unless I use the 'Save for Web' feature.

[HackerX]

Hmmm, I suppose since I don't use photoshop, it just never occured to me.

I think photoshop allows for uncompressed jpegs though, which would inflate the size of the file a lot. But you'd know better than me if that's the case.

[Jezebel]

I think photoshop allows for uncompressed jpegs though, which would inflate the size of the file a lot. But you'd know better than me if that's the case.
There is little if any noticeable difference between the compression methods, at least visually. The default Photoshop save feature adds an 'invisible layer' of information to each file containing metadata, markers, and other such things. While this information does have useful applications, it's a lot of useless bulk in web images when the goal is a small file size. The Save for Web method allows users to omit those things to achieve a smaller size.

[AliTree]

It's because INTJf has limited bandwidth and right now we host everything on-site. Increasing the avatar kb any substantial amount would cost money, otherwise I would gladly raise the limit. Have you read this thread (http://intjforum.com/showthread.php?t=7915)? If you don't have Photoshop or have any other problems, I can get the color images to the appropriate kb with minimal quality loss.

ahh. that would make sense. and i just read that, but i don't have photoshop. i do have photofiltre, though. if you know how to do the same for that, i won't waste your time and edit the image myself.

[Harmony]

Nah, using the standard save feature in Photoshop often gets jpegs around two to three times over our requirements. I can't save them under 19kb without a lot of ugly compression artifacts unless I use the 'Save for Web' feature.

You may have just saved me from throwing my laptop out the window. =P I use Photoshop and even at the lowest possible setting it was too big. =P

[Sesshoumaru]

You may have just saved me from throwing my laptop out the window. =P I use Photoshop and even at the lowest possible setting it was too big. =P

You could always try saving as GIF as it uses less of a color palette. It's what I had to do.

My avatar was 33 or so kb as a JPG (Quality 10) and 16 or so as a GIF...Not too much noticeable quality degradation either.

[lamplighter]

When using the "Save for Web" feature think about the image being saved. PNG-8 is what you need to use for anything with a transparency and offers a wider color pallet than GIF and usually saves as a smaller size, PNG is also better than JPEG for anything that requires sharp contrast like drawings or text, and is a lossless graphic format like GIF. JPEG however can be saved in an even smaller format than PNG and great for anything that has a lot of gradients in it like photographic images, but will suffer from generation loss. It could've been the larger color pallet the image required or it could have been that you were saving in an interlaced JPEG format as to why the GIF was smaller.

[Sesshoumaru]

When using the "Save for Web" feature think about the image being saved. PNG-8 is what you need to use for anything with a transparency and offers a wider color pallet than GIF and usually saves as a smaller size, PNG is also better than JPEG for anything that requires sharp contrast like drawings or text, and is a lossless graphic format like GIF. JPEG however can be saved in an even smaller format than PNG and great for anything that has a lot of gradients in it like photographic images, but will suffer from generation loss. It could've been the larger color pallet the image required or it could have been that you were saving in an interlaced JPEG format as to why the GIF was smaller.

I don't know if IEs changed...I don't use it and haven't for ages...but doesn't it not support PNG transparency.

[lamplighter]

I don't know for sure since I use Firefox, but Firefox has (the reason why it's not allowed here) since at least 2.x and is at 3.0.5 now. So I would imagine Microsoft would have implemented PNG transparency in the current build of IE to stay competitive.

[WaeV]

I always use png format. It has much better quality than jpeg, and with the "save for web" feature of photoshop it is of comparable size (not to mention available transparency). On forums that allow signatures I have a rotating set of 400x96 pixel sigs, and none of them are over 30k.

[nowandzen]

Using Photoshop I have been unable to get my custom 115 x 145 pixel avatar below 23kb. Any tips on how to make the file size smaller would be appreciated.





nowandzen added to this post, 2 minutes and 16 seconds later...

I always use png format...

Oh oh, thanks!

[Zombicide]

If anyone is having trouble with number of pixels, you can zoom in using something like e.g. MS paint in order to manually count and manipulate the number of pixels. If for some reason you are having trouble seeing the pixels directly after zooming in, you can always draw temporary diagonal lines to help you check.

I find you can quickly lower the KB very much by making the image a screen capture, of course it will only reduce the quality as much as a screen capture normally is reduced i.e. not immediately noticable. I think my ideas I figured out in making mine are good if you do not have Photoshop.

[HackerX]

If anyone is having trouble with number of pixels, you can zoom in using something like e.g. MS paint in order to manually count and manipulate the number of pixels. If for some reason you are having trouble seeing the pixels directly after zooming in, you can always draw temporary diagonal lines to help you check.

Hmm? Even Paint has a ruler you can use. In the status bar it will tell you the size of the image (Width x Height).

If you use the rectangle selection tool, that status bar will switch to tell you the size of the section.

[jonkun227]

For those having trouble meeting the file size requirements, here's a technical explanation of image files that should help:

Most images you've ever dealt with were 8 bit or lower. That is, 256 levels of brightness per channel. Most you've dealt with were 3 channels or fewer, usually RGB. So 256 values of Red, 256 Green, and 256 Blue.

HOWEVER, the file size is not on a linear scale. It's logarithmic, if I remember my math terms correctly. (I'm more photographer than mathmagician, so correct me if I'm wrong on the term.) Fully half of the data is used to store the brightest values, as those are the ones our eyes can best resolve. Half of the remaining data is used for the first darker bracket, then half again for the next, and so on.

What this means is that an image that contains any bright values, much less predominately bright values, will produce a larger file size than a darker image of the same proportions and detail.

The other factor is that the higher the detail the larger the jpg file, as the jpg compression attempts to retain detail, but at a cost dictated by the compression level.

Try this to understand what I mean: take a photo with your digital camera on a standard jpg setting, of a detailed scene. Now take the exact same scene with a substantially darker setting. I won't take the time here to explain how, just figure it out if you don't already know. (As an INTJ that should only take a few moments.) Now compare the file sizes.

Now repeat the procedure with comparable brightness but substantially different details. First a busy scene, then a blank wall of about the same brightness. Compare file sizes.

Applying that to your avatars, you'll understand that if you are hitting the file size it's probably because your image is too bright and detailed. Darken it, blur it, or change it altogether and it will fit.

[WaeV]

Interesting, i didn't know that about jpegs.

But I prefer lossless formats such as GIF or (even better) PNG.

[sybiam]

HOWEVER, the file size is not on a linear scale. It's logarithmic, if I remember my math terms correctly. (I'm more photographer than mathmagician, so correct me if I'm wrong on the term.) Fully half of the data is used to store the brightest values, as those are the ones our eyes can best resolve. Half of the remaining data is used for the first darker bracket, then half again for the next, and so on.

It doesnt work like that....Colors are indexed...if you have a lot of color that look the same...you'll have a smaller size...If you have a lot of different colors...the compression will be bad.

No matter how bright or dark a color will be...it will always take the same amount of space...Bright or Dark...it will be on 8 bit no matter what.

let say we have a RGB file each color with 8 bit each pixel would use 24 bit.

if each pixels are to 0x00 0x00 0x00 (black) and 0xFF 0xFF 0xFF (white)...each pixel no matter how bright they are will take the same amount of space...(you can try it. Take a white and a black picture. I get 1.5ko for each files)

I then added equal black and white shade on each pictures. Each file were the same size about (3.5ko)

The thing is.... the white square is actually a picture of this size (640x400) taking only 3.5ko of space. Why?

because there is only 2 colors...and there is only may be 2% of a shade...

So from what i know about file compression...
1. More colors equal bigger file size
2. Less colors equal bigger file compression
3 .Different shade doesn't change anything unless it creates more color or more different shades...

Thats why on a dark picture, the file might be smaller as there is less different color...
On a bright picture you will see more color...But imagine you take in picture something really bright like a white wall or a green wall...and there isn't much different color. the file size should be smaller because the file is easier to compress without loosing quality.
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Unless you have some proof about what you said...I'm not too feeling to look at the code of jpg compression...:/

[jonkun227]

What I'm talking about isn't unique to JPG compression. In fact the JPG compression complicates the situation because it's able to compress efficiently when the tones are that consistent.

And JPG isn't indexed. GIFs are indexed, but JPGs aren't. They are compressed in blocks of 8x8 pixels, each block treated individually, which is why every digital camera has a pixel dimension divisible by 8.


- Jon