Image quality refers to the characteristics of an image that assesses the perceived level of degradation or perfection. Typically, an image is considered ideal or perfect based on its quality. The imaging system of a photo can introduce some degree of distortion in the quality through such processes like trans-coding which subjectively interfere with the quality of the end user. In most cases, the quality of a photo is primarily determined by the camera and the photographic process. However, the process of transmission and storage may require compression and decompression thus interfering with the quality features.
Image Forming Process
An image is normally formed on the plane in the camera and then processed electronically or chemically to display a photograph. The ideal pinhole camera can be used to describe the ideal formation of an image where light rays from the object passing through the camera aperture and on to the image plane. The quality of the image may also be determined by how the camera configures the pinhole model. Thus, when a camera captures the light from the object, it should be reflect on the image quality.
Images are comprised of small dots known as pixels which represent a combination of three primary colors (red, blue, green). High image quality has more pixels while lower image quality has fewer pixels on the same image size. A large or high quality image has many pixels and also requires huge space to store or transmit through a computer. Computers have a way of compressing images to fit in the available space or to transmit through the available bandwidth which is then decompressed on the other end.
Resizing Image During Transmission
When an image has 10 megapixels, it would require 30 million bytes or 30 Mbs at each stage to store, send and be downloaded. The size of this image can be compressed to minimize the file size and resize the photo size. However, the quality may be affected upon successive compression as the image losses more data. Reducing the image size does not reduce the image quality of the photo although it may lose some finer details when it becomes too small.
Images captured using digital cameras usually have about 6 million pixels while tablets and TV screens have about 1.5 million pixels. This implies that when an image is captured using a phone but then displayed using the TV screen; you end up seeing a resized (enlarged) version of the photo that may also look blurred. When the photo is resized to fit the width and height of the original screen, the picture is displayed in the same number of pixel in the camera hence it does not lose its quality or details.
Lowering Image Quality
Image compression is normally performed to reduce their cost on storage and transmission. There are various algorithms that are applied to maintain the statistical properties and visual perceptions of the image data to provide the user with better results that are not available in generic methods of compression. Lossless data compression can also be preferred for storage purposes especially for medical images and technical drawings. Lossy compression methods are more appropriate for natural images like photos where minor loss of fidelity to achieve substantial bit reduction is acceptable.