Optimising

Target image output
If you want to get the best image possible, you should be aiming for the best image output. Depending on your t.v. the best image output will vary. But if you have a HD TV the best possible setting is 1080P.

Image bit depth
Bit depth is the number of bits used to show the colour of a single pixel in a bitmap image. The more bits there are the better the image. Therefor you should want as much bits as possible.

Image resolution
Image resolution describes the detail an image has. Higher resolution means more image detail; therefor you want as high resolution as possible. Image resolution is important if you need a large image but if the image is being used with memory in mind, file size might be an important consideration.

Image dimensions
Image dimensions are the width and length of a digital image. It is more commonly measured in pixels, but some programs allow you to view and work with your image in the equivalent inches or centimeters. If you are using a high resolution digital photograph, you should probably make the image dimensions smaller. Where as if you are using a graphics or image-editing program you will have two options for changing the dimensions: Re sample or re size.

Compression
There are two types of compression, lossy and loss less. Lossy compression is a data encoding method that compresses by getting rid some of the data. Which means when it gets re sized it wont look as good as before it was shrunk. Loss less is effectively the opposite, it allows the exact original data to be re-made from the compressed data.