Image formats

Pages: 12

Mar 20, 2010 at 8:02pm

I was bored so I came up with this list of the only image formats I think are worthy of existance.

PNG (Portable Network Graphics) (pronounced: ping) (.png):
PNG is my favourite image file format because

- Has a fantastic compression ratio (better than JPEG sometimes)
- Brilliant quality (better than GIF, FAR better than JPEG)
- Alpha channel (transparency) (JPEG has no alpha channel)
- Interlacing
- Widely supported by web browsers

SVG (Scalable Vector Graphics) (pronounced: S-V-G) (.svg):
SVG is an extremely useful image format:

- One-size-fits-all
- Can be hand-written (XML)
- Alpha channels

But there are also problems with SVG:

- Because SVG files are plain-text XML files, they cannot be compressed
- SVG files are dynamically generated based on XML; so the XML has to be
- Tokenized
- Parsed
- Turned into a bitmap file
- Displayed

TGA (Targa) (pronounced: Targa) (.tga):
To be honest, the only thing I like about TGA is that it's supposedly very
easy to implement.

GIF (Graphics Interchange Format) (pronounced: Jiff) (.gif):
Again, the only thing I like about GIF is that GIF files can contain animations.
I don't think any other formats can do this.

What are your opinions?

Mar 20, 2010 at 8:18pm

closed account (z05DSL3A)

I would include JPEG2000, far better than PNG.

Mar 20, 2010 at 8:27pm

chrisname (7395)

Does it have interlacing and alpha-channel support?

Mar 20, 2010 at 8:34pm

closed account (z05DSL3A)

Yes, and yes.

http://en.wikipedia.org/wiki/JPEG_2000

Mar 20, 2010 at 10:21pm

NGen (689)

Looks very difficult to implement...

Mar 20, 2010 at 11:15pm

Bazzy (6281)

GIF --

Last edited on Mar 20, 2010 at 11:15pm

Mar 21, 2010 at 12:16am

chrisname (7395)

Is that a decrement?

Mar 21, 2010 at 12:25am

Bazzy (6281)

yes. I know it doesn't look good

neither GIFs or my previous post

Mar 21, 2010 at 12:30am

chrisname (7395)

You forgot the
-moves head in z shape while clicking fingers and humming-

Mar 21, 2010 at 12:49am

Duthomhas (13277)

JSYK, text files typically compress better than binary data.

I like TGA, but it has the fabled file types 32 and 33, which don't exist. (I've asked Truevision for information on them, but they don't care.) Sooner or later I'll post some TGA code on Sourceforge that implements a type 32 compression so everyone can use it. :-)

Lack of serious compression is what really hurts TGAs.

TGA is much more flexible than people give it credit for. However, there are certain reasonable conventions that keep it fairly narrowly defined. It is very easy to write a decompressor for it, particularly if you plan to keep to a specific class of input types.

GIF is also a very nice compression format. Unfortunately, everyone believes it is limited to 256 colors, and as a result it is very restricted in industry use. Modern browsers will tend to do things to a GIF display that it shouldn't when given truecolor input file.

I like PNG, but besides writing a decoder for it I've not played with it too much.

PNG beats the pants off of GIF in compression ratios. (5% to 25% better file size -- my own testing averaged at about a 20% improvement.)

I know nothing about JPEG2000. It appears to be much too complex for my liking. I don't like a lot of overhead... (Which is why I like the first three so much.)

Also, don't forget TIFF. It is heavily used in the industry, and cannot be discounted. Unlike any other format mentioned here, TIFF has support for useful color spaces. It is, however, a really bastardized beast, and so becomes an awful burden to support.

I just visited http://en.wikipedia.org/wiki/Image_file_formats to see if I had forgotten anything, so I'll just leave it for you to visit. The only thing I notice there is that the page replicates the error about GIF supporting only 256 colors...

Ultimately, each format exists because of the domain for which it is useful. If I were working to produce trading cards for the next Pokemon set, I wouldn't use anything but TIFF. If I were a photographer, I would stick with JPEG or JPEG 2000. Web developers will stick to GIFs, PNGs, and JPEGs. Graphic designers will use SVG or other vector formats. For each case, using something else would be like trying to shoe a horse with a rubber tire. It makes no sense.

My $0.03

Mar 21, 2010 at 2:10am

Disch (13742)

I don't think any other formats can do [animations]

MNG, APNG. Though neither are as widespread or established as GIF.

I would include JPEG2000, far better than PNG.

You can't really say this. I mean it's not fair to either one.

JPEG2000 is lossy
PNG is lossless

The two have entirely different applications.

EDIT: actually I guess JPEG2000 can do lossless to. I didn't realize that. Still it doesn't seem to do lossless quite as well as png.

Last edited on Mar 21, 2010 at 2:11am

Mar 21, 2010 at 4:55am

helios (17607)

Because SVG files are plain-text XML files, they cannot be compressed

Sure they can. It's called SVGZ.

I find the lack of JPEG and raw in this thread, disturbing. JPEG does great for photographs and any picture without sharp edges. There's few things I hate more than seeing someone uploaded a photo as a 2 MiB+ PNG.
And raw is great when you just need a simple format for temporary storage. I use it to cache rendered SVGs to disk, since it's usually a lot cheaper than keeping the loaded SVG around (a 150 KiB SVG can explode to over 70 MiB when loaded. Keep in mind this is regardless of whether it renders to 32x32 or 3000x3000).

And what's so great about interlacing, anyway? I've always hated progressive JPEGs and interlaced PNGs. If I have to wait a little longer for the next scanline, so be it, but I very much prefer it to getting it at 1/16 resolution.

Mar 21, 2010 at 4:58am

Disch (13742)

And what's so great about interlacing, anyway? I've always hated progressive JPEGs and interlaced PNGs.

Truth. Interlacing sucks.

Mar 21, 2010 at 5:40am

chrisname (7395)

I didn't say interlacing was great. I just said that PNG had support for it.

Alpha channels, on the other hand, are great: http://upload.wikimedia.org/wikipedia/commons/a/a7/Hue_alpha.png

Mar 21, 2010 at 8:28am

closed account (z05DSL3A)

Disch wrote:
You can't really say this. I mean it's not fair to either one. JPEG2000 is lossy PNG is lossless

The JPEG2000 standard provides both lossless and lossy compression in a single compression architecture.

Mar 21, 2010 at 6:01pm

Duthomhas (13277)

Interlacing is a Good Thing.

The rationale for interlacing is very straight-forward and reasonable. The PNG specification itself gives a very good explanation that is worth reading again.

Mar 21, 2010 at 6:22pm

chrisname (7395)

By the way, my reasoning as to why SVG files shouldn't be compressed is because they're plain-text. If you compressed them, the best thing (IMO) about them (that they're human-readable and human-writable) would be gone.

@JPEG,
Uhhh, no.

As for raw BMP; I was going to mention it but I forgot. I think it's good because it's simple and it has alpha-channelling; but raw bitmaps are also very large. I have eight small PNG images in a folder and together, they are 2.8 kiB in size. As raw bitmaps, they total 916.8 kiB and as JPEGs, they total 9.2 kiB and the quality is horrible.

Mar 21, 2010 at 7:25pm

helios (17607)

they're human-readable and human-writable

Yeah, totally.

Last edited on Mar 21, 2010 at 7:26pm

Mar 22, 2010 at 12:51am

chrisname (7395)

I assumed that because they were XML they would be more... sensical. My mistake.

Mar 22, 2010 at 2:24am

Duthomhas (13277)

What's wrong with JPEG?

It is well-thought out and well-designed. It also provides a lot of flexibility when compressing.

(Just because some people produce horribly compressed JPEGs is not a valid argument against the format. For that matter, bad BMPs aren't an argument against the format, only against the person who created the image.)

RAW, BMP, and TGA are all relatively uncompressed formats. They are very friendly for intermediate storage and simple readers.

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