h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Bitmap File Formats - A12042325
Author: The_Jon_m - Scout, I am the only and only, nobody I'd rather be. Wibble - U204330

hello

herewith the bits I don't understand:

The big advantages with vector formats are that everything is scalable and editable. If you want to double the size of the image, a draw program can redraw the image double the size and every object will increase in size and remain as crisp as it was at half the size. If you save it again, the file size will remain the same.

Why? How does that work?

poop, I've run out of time, but I'll be back - this fascinating.

Nice, I'll link your entry to mine.

a couple of nitpicks...

"‘ Draw a square"
there's a space there that you don't need.

"A some formats" I'm not quite sure what this should be...

"first two images formats" images? not sure on this one.

" you a little bit of detail." lose.

" because they loose too much detail" again, lose. ( i think)

" (it can deal with 48 bit if you push it)" I don't understand. How do you push it? or am i too literal?

"some paint programs have difficulty optimised PNG files" optimising?

" Abode Photoshop" Adobe


but i've learned a lot from this entry!

Traveller in Time writing slow
"The subject title is Bitmaps, nut you start off with a conciderable mount of Vectors. (I always take true type characters and fonts as the ultimate example of vector items)

>Also every operating system has a simple ‘Paint’ program that will produce bitmap images

Well I remember (and still work with) command interface Operating systems like DOS. Perhaps rephrase it as 'Graphical Operating Systems'

>There is no way now to edit the square. Rotating or increasing the size of a bitmap image will result in a loss of quality.

Completely wrong. doubling the size does not give a change in quality, nor does rotating over 90 degree angles.


>5,000,000
five million < Subeditors-Style > And I think it will be more likely to be 4,915,200 byte (2560* 1920) using 24 bit per pixel will need 14,745,600 Byte.


Pixel >> Picture Element ( PICture ELement )


>They undergo no compression, no fiddling with.
I would not call compression fiddling . . . missing second subject.
Images (and sound) use lossy compression rather then normal compression as required for executables or text.

>Bitmap format are native for MS Windows.
>>Bitmap image format are native for MS Windows.
There are more bitmaps inside your computer most are used inside programs but they have nothing to do with images.

The file is mostly of type BMP, though the format is so called Device Independend Bitmap DIB is sometimes also used as file extension.

BMP does know of compression, though not always used the bmp format can contain a compressed image. (There are codes for compression in the header)

Most used compression for bmp Bitmaps is the use of a pallette, only the used colours are coded with the RGB (Red Green Blue) nibble or byte values. Then the 256 colour map uses the palette colours to give the positions. The bmp images are stored upside down.

PCX >> Personal Computer imageX something . . .

The limited colour depth in a gif image is a lossy compression !

AniGif >> six images in brunel twelve in Goo.

A JPG image is build up out of blocks with vertical horizontal or diagonal gradient ranging from one colour to another. High compression levels can be achieved as low detail parts of the image can use large squares while high detail areas can use small squares.

Also explains the compression difference:
>Bright, sharp, complicated images such as do not compress well.

"

>>Completely wrong. doubling the size does not give a change in quality, nor does rotating over 90 degree angles.


if you increase the size of a bitmap, then it will become more pixelated since you only have a certain amount of pixels to expand, and you can't create new detail in a bigger image.

if you rotate an image over most angles (not 90 / 180) then it has to resample, and it will lose some detail.

Traveller in Time calculating resolution
"
>If you increase the size of a bitmap, then it will become more pixelated since you only have a certain amount of pixels to expand, and you can't create new detail in a bigger image.

Exactly like you say: 'you can't create new detail in a bigger image', so there is no loss or incrase in quality. Vector images increase in quality when _Objects_ in the picture are enlarged.

Rotating the image with a small 'paint' program will give bad results, there are more sophisticated programs however. "

Here's some information regarding TIFF files that address the question (which has not been asked) of what to do when you want to tile many bitmaps together - as for example Map Google does to show a composite satellite image of an area. So here's a bunch of information that you can cull down to "Tiff files have other mostly harmless uses" if you like:

TIFF files are also the coin of the realm for Graphical Information Systems (H2G2 reference A313264) that, among the many other technical things they do, can take individual bitmaps of portions of a city (for example) and arrange them together into a sensible cityscape. In this case, each TIFF file will have an auxiliary file with the TFW extension, which is called the World File - it contains the necessary information to properly Geolocate (possible H2G2 reference A7078827, but...) the image - that is, it tells how to scale the image (how many meters each pixel is on a side), and at what (usually, earth based) coordinates the lower left corner corner of the bitmap should be placed.

That's it - good entry

oops, change that from "lower left corner" to "upper left corner"

Hi The_Jon_m,

I agree that, for an entry on bitmaps, it seems odd that ther first three paragraphs are concerned primarily with vectors

The fourth para starts "Bitmaps are much easier to use" - but you don't say why

Where you say
> they are also the type of picture that most people are familiar with
I suspect you mean
>> they are the type of picture that people are most familiar with


As TiT rightly pointed out, it's only every GRAPHICAL OS that has a simple ‘Paint’ - I guess that many/most people will infer that... but OSs are built into a variety of tools without any visual interface, so it is misleading - all for the want of one word

> with the growing use of The Internet
>> with the growing use of the Internet

> and digital camera
>> and digital cameras

> we see more bitmaps in everybody life
>> we see more bitmaps in everday life

> The major problems with bitmap images are size and ease of editing.
> The major problems with bitmap images relate to file sizes and editing techniques


> certain pixels are now blue, rather than white
I honestly don't know... I'm simply wondering here... isn't the default 'black' (R=0, G=0, B=0 - hex 000000)?



>There is no way now to edit the square
not quite... you can recolour it...

> Rotating or increasing the size of a bitmap image will result in a loss of quality

>> Rotating (by anything other than 90°, 180° or 270°) or increasing the size of a bitmap image will result in a loss of visual quality



RAW format

Another big disadvantage of RAW is that there are 100s, possibly 1000s of 'dialects' that store image and 'camera setting' data in differing ways. The data is encrypted and the only way to gain *full access* to the images stored in your own files is to use the software sold by the camera manufacturer...

Problems will arise when (not if), as time passes, the manufacturers discontinue support for their 'old' products and when (again, not if) bugs appear in the software


> GIFs
>
> Loss-less image compression means that no image detail is lost in the compression.

This might be an opportune point to mention that if you're 'borrowing' images from the Internet, specifying filetype:GIF in your search string might save a shedload of time when editing



>anti-alising
>> anti-aliasing


>JPEG or JGP
>> JPEG or JPG


> most evident is on blocks of solid colour, where ‘artifacts’ are quite obvious.



> JPEGs are best for storing photos or images with lots of gradients and little or no block colour. While they are fine for storing photos on own computer or for putting on the web, they are of little use for printing

How about something on 'saving for the web' settings - the ones I wish I knew about *before* I uploaded my first gazillion photos

> but until version 7, Microsoft Internet Explorer
how come the profanity filter lets that through?

> TIFF files don’t display on web browsers.
Wow! They right! You learn something every year!







OK... other than that, I reckon this has the makings of a great guide entry

Traveller in Time confused by black blue and white
"Must have missed the reference.

>When you place a blue square on a bitmap image, the program records that certain pixels are now blue, rather than white. When you open the file up, you see a square, but the program only sees that some pixels are a different colour. There is no way now to edit the square. Rotating or increasing the size of a bitmap image will result in a loss of quality.

This whole paragraph, is discribing the behaviour of one particular bitmap manipulation program rather then properties of 'Bitmaps'.

But perhaps my view of bitmaps is more from the inside then from a user application point. "

I don't know if you know this already, but there are numerous spelling errors in the entry.

Hi Jon.

Are you happy with this entry now?

Regards

VV

no, I have to edit this still however I have just moved house and am currently to confuzzleed to try and decode TiT and reedit my doc, will wait till the weekend

Traveller in Time searching for some image manipulation programs
"Not defined pixels are not defined, the program you are using to draw gives them a default colour, there is no default in the definition of bitmaps. "

You forgotten about this one jon?

no, I'll finish it on Sunday

updated

Good entry - a few things I spotted on a quick read through:

>The most popular of these are CorelDraw, Illustrator and Freehand.

I expect these are Tradmarked - does that need to be reflected? Is it also worth stating which company these come from?

>If you save it again, the file size will remain the same. Since every object is saved as its own instruction, they are also completely editable when you load up the file again.
-> If you save it again at the new dimensions the file size will remain the same, since every object is saved as its own instruction. They are also completely editable when you load up the file again.

>In recent years Standard Vector Graphics (SVG) and Vector Mark-up Language (VML) have been rolled out on the web, but take up has been poor.
-> In recent years Standard Vector Graphics (SVG) and Vector Mark-up Language (VML) have been rolled out on the web, but implementation in browsers has been poor so they have not become popular.

>The major problems with bitmap images are file sizes and editing techniques.
->The major problems with bitmap images are larger file sizes and more complex editing techniques.

>when you reduce the size of a bitmap you loose detail in the image.
->when you reduce the size of a bitmap you lose detail in the image.

>Lets say with have taken a holiday snap on a digital camera. Let’s say it produced a five mega-pixel picture; that is a picture made up of about 5 million pixels.
->For example, a photograph taken on a five mega-pixel digital camera is a picture made up of about 5 million pixels.

What are RAW, BMP and PCX acronyms for? You have expanded GIF, JPEG, etc.

I think the debate about the pronounciation of GIF should be near the start of the section (I never understood the reason for debate g is for graphical, therefore must be hard).

>If you are working on an image, it is best not to keep saving your image as a JPEG. Each time you save an image then load it up, you loose a little bit of detail.
->If you are working on an image, it is best not to keep saving your image as a JPEG. Each time you save an image then load it up, you lose a little bit of detail.

The stuff about vector graphics at the start is very heavily biased toward the amateur user. It kind of mentions a few home-PC drawing packages and then dismisses CAD as an "also". Surely CAD is the raison-d'etre of vector graphics, and therefore by far the most important application of it. Most CGI is vector-based I believe. Also, the vector formats used by CAD programs are pretty interchangeable nowadays (dxf, dwg).

JPEG is not a file-format; it is a committee. The format is defined by ISO/IEC IS 10918-1 / ITU-T Recommendation T.81 according to their site:

http://www.jpeg.org/jpeg/index.html

I think the rest is fine as it is - I fully understood and agreed with your explanation of increasing size - decreasing quality.