Easiest and non-destructive (means you can change settings at any time after applying them even after saving and reopening image) way is to use Brightness/Contrast adjustments from Adjustments panel (Window > Adjustments) or go to Layer > New Adjustments Layer > Brightness/Contrast.
Photoshop is a commonly used professional image editing software. I would recommend this.
Curves-Auto,Curves are adjustments you can access from Image-Adjustments-Curves in Photoshop
The best way to center your image would be to use programs such as Photoshop and Gimp. They work wonders when you are working with pictures that you would like to edit.
You can artificially increase the resolution of a jpeg image in Adobe Photoshop, but there will be a loss in quality because data is "invented" through a process called interpolation. A low resolution image only contains X amount of data, and to increase its resolution, you are telling the computer software to add nonexistent data to the picture file. This is generally ok if you're only increasing the resolution by 10% for general print purposes, but to make a dramatic increase in resolution such as 72 dpi to 300 dpi, the image will most likely artifact (pixelate).The best and obvious solution would be to acquire the original image.
Gimp is nothing like Photoshop. It works with images in a way that is completely foreign to those familiar with Adobe-type products. It was as if it the program was designed by someone who had never had to actually manipulate an image professionally. If you're stuck on the Linux OS, but you need to work with images I would suggest looking at an app called "Pixel Image Editor". Also, there is a Gimp/Photoshop hack called "Gimpshop".
If the green pencil is moved farther away from the mirrors, the size of the image would decrease. This is because the image distance would increase, causing the image to shrink in size.
You can Anti Alias either fonts or vectors shapes only ... if you bring in your own image, let's say by copy and paste, your best bet would be to blur the edges. See: "Photoshop Feathered Edges" in google search.
First click on layer with pixels you want to warp (layer can not be background layer, must be regular layer), in Photoshop CS5 and newer go to Edit > Puppet Warp or Edit > Transform > Warp.
Its not Photoshop PNG but rather PNG-8 file format. Use it to save files with limited color palette (max 256) to have file with smaller size for Web which can contain and transparent areas in image.
An Adobe Photoshop tutorial about the pen tool teaches one how to use this tool to make selections. The selections start with something called a path, which is basically a straight or curved line connecting two points in the image.
It will depend on the photo software that you are using. Photoshop has a "stamp" tool that would be helpful, but it depends on a lot of things. How large is the garbage can image in the photo? Is there (or would there be) a lot of complex detail in place of the image, etc. Perhaps a friend with Photo software could help.
I would strongly recommend you upgrade to the newest version out which is Photoshop CS5 if you can.And it's Adobe Photoshop CS2. You wont find any answers typing CSS2.