Understanding Graphics

PSP
Trying to...Understand Graphics

General - tut - Darkstar



Graphics, and file formats and their use, fills many, many books.
Big...Thick...Books.

So I will try to give you some GENERAL guide lines.
(But this is still long)

The First Thing is ...
EVERY picture has a fixed amount of pixels(or dots) in it that makes up the picture.
3 things determine the Picture.
The height...width...resolution.
All 3 combined make up your picture and the amount of pixels in it.
If ANY one of the 3 dimensions change, the others change.

About Re-sizing

Remember height/width/resolution make up your picture.
There is only so many pixels to start with.
When a picture/graphic is re-sized (either height/width/resolution) it is done basically one of two ways.

Either it re-samples or it doesn't re-sample it.

Basically "re-sample" means to make up...or take away pixels as needed to get the NEW size you want.

Graphics programs like PSP (Paint Shop Pro by Jasac) or Photoshop (by Adobe)will give you the option to re-sample or NOT re-sample.
Most other programs that can re-size a graphic, automatically re-sample (make up or take away pixels) no matter what.

Now, making a graphic/pix smaller (either height/width or resolution)takes away pixels (if re-sampled) and is usually not very noticeable.

BUT....if a graphic is re-sized (re-sampled)... larger or UP-sized...it has to MAKE UP pixels.
When a picture/graphic is UP-sized AND re-sampled, you start loosing quality and sharpness, and THAT is why a graphic starts not printing well.
How the graphic STARTS OUT, or the width/height/resolution, it ORIGINALLY has, is important.
(We will do some examples soon)

Graphics and pictures used for the WEB...

I will touch on this as it helps to see the whole story.
Many, or most of the graphics you see on the web are WEB graphics.
By that I mean they are smaller in SIZE height/width and LOW on resolution, usually 72dpi.
The reason is, a computer monitor IS low-resolution and can't use the extra resolution anyway. That also helps the FILE SIZE be much smaller, which is a big deal for use on the web.
Also..file format, like gif, was designed for WEB graphics and for animation and is NOT a good file format for print.
(More on image formats later)

jpg is a compressed format that CAN deliver a "quality rating" of 1-12 or low/med/high. That makes the FILE SIZE smaller for web use, or better quality (and larger file size)for print.

*** MOST all graphics you RIGHT click and save on the web are likely LOW-res WEB graphics and just are NOT going to print well. They just don't have the pixels.
(remember the height/width/res thing)

PRINT graphics...

To Print graphics, the graphics need to be MADE at a higher resolution, and larger size (height/width) in the first place.
(Many graphics are b@%/ed as printable. But are either to small SIZE wise or low resolution...or both)

*** THE KEY THING ***
When using graphics for print...you want to avoid re-sizing a graphic UP (make larger) as THAT is what gets your graphic looking bad.
(File format also matters-will get into that also)

When BUYING or MAKING graphics..look for graphics around 200-300 dpi AND a decent size height/width wise.
OR
If they are 72 dpi graphics/pictures (like what a digital camera gives you)that the SIZE (height/width) is large..in fact very large, like 12 inchs or more.
That does NOT mean that because it is 12 inchs and 72 dpi that you can print a good 5x7 or 8x10.
Remember height/width/resolution determines the amount of pixels in that picture.

Example:
If you had a picture that was 8 in x 10 in at 72 dpi.
If you re-sized this to 300 dpi WITHOUT re-sampling or making up pixels.
In other words..make this picture 300dpi with the pixels you have...do NOT make up anything then the image becomes
1.92 in wide by 2.4 in high at 300 dpi.
Now THAT is your printable resolution, but as you see, it is much smaller height and width wise.

That is why if you told it to re-sample it,(make up pixels) that is making up a lot of pixels...and that is what most programs do.
Your 8x10 @ 72 dpi has to make up a whole lot of pixels to get that 300dpi AND keep the 8x10 size.
This is why graphics look bad when re-sized UP.

REMEMBER.the idea is to either purchase or make higher resolution graphics, so that you don't have to UP size much.

Now the formulas that re-sample, or make up pixels, are pretty good...but your pictures will degrade.
You can NOT make a small, low-res graphic into a higher resolution or size without loosing sharpness and quality.

FILE TYPES...

The file format you have your graphics saved as makes a difference on the ability to re-size, and print.

JPG- A good general format-but it is a compressed file format.(it does NOT keep all the data). File size is smaller and you can usually pick a quality of 1-12 or low/med/high.
Does NOT re-size well. If you need a smaller file size and you use a higher quality setting, it is a pretty good format.
BUT...every time a jpg is re-saved it will loose quality.

GIF- does support transparency, but really its use is for WEB graphics and animation. Not really a print format. It ONLY supports 256 colors, so use would have to be for simple graphics.

PNG- best choice for files with transparency. Will re-size well, but larger file size.

BMP- best for graphics (without transparency). re-sizes well. Larger file size.

TIF- best for photos (can support transparency in some programs) Re-sizes well. Large file size.
If you want a permanent back-up of a photo that you may need to use over someday. The TIF is your best bet..as it retains ALL info unlike the jpg.