Question I
Joint Photographer Experts Group (JPEG)
- The Joint Photographic Experts Group (JPEG) file format is considered to be the best way to compact photos for use in web publication. This is because JPEGs save these images in 24-bit color while GIFs only use 8 bits or less. This allows saving of the rest of the colors. Accordingly, JPEGs are much suitable for photographs and images which use fine frequencies the combination of tone and color.
Most digital cameras also use the JPEG format to store images. JPEGs use a type of compression technique that which removes unwanted image data. This compression method used is the lossy compression method. In most cases, the more times that an image is compressed the more chances for the compression method to create artifacts. These artifacts are the unwanted distortions in the image. So every time an image is saved as a JPEG some of the data from the image is lost accordingly.
Tagged Image File Format (TIFF)
The TIFFs main strengths lie in its highly flexible and platform-independent format which is supported by numerous image processing applications. Since it was designed by developers of printers, scanners and monitors, it has a very rich space of information elements for colorimetry calibration, gamut tables, etc. Another feature of TIFF which is also useful is the ability to decompose an image by tiles rather than scanlines. This permits much more efficient access to very large imagery which has been compressed (since one does not have to decompress an entire scanline).
Some common objections on the use of TIFF method is on its capability for saving vector graphics, text annotation, etc. Since TIFF method is saved as file-offsets this causes it to be no as easily stream able in the way JPEG streams are.
Graphics Interchange file Format (GIF)
GIF is considered best for computer generated images with limited palettes. This is when a large area of uniform color and the total number of colors is smaller than 256 is present. With this kind of setting, GIFs can make flawless copies at high compression as long as the image contains large areas of uniform color, and as long as the image has no more than 256 colors. As of recent, most web authors nowadays prefer to use the PNG file format since this format is not limited to the 256 total number of colors to which the GIF is limited to. Furthermore, the PNG file format saves the image at a smaller file size compared to the GIF, and PNG is not limited to 256 colors as is GIF. The only reason to use GIF is for images with transparency.
Question II
Lossless compression
Lossless compression refers to the type of data compression technique wherein which no data is lost in the compression. For most types of data, lossless compression techniques can reduce the space needed by only about 50%. To achieve greater compression, it is suggested to use other methods of compression. Note, however, that only certain types of data — graphics, audio, and video — can tolerate lossy compression. It is also considered wise to use a lossless compression technique when compressing data and programs.
Furthermore, lossless compression technique is classified as a class of data compression algorithm which allows for the exact original data to be restored from the compacted data. This method is clearly in contrast with lossy data compression.
Lossless compression best used when it is crucial to original and the decompressed data to be identical with each other, or when no presumption can be made on whether certain changes are considered irrelevant. Some examples of this type of compression are those used in are executable programs and source codes. Moreover, some image file formats which use lossless compression include PNG, use only lossless compression. GIF uses a lossless compression method.
Additionally, lossless compression methods are further classified according to which type of data it is designed to compress. These three main types are: text, images, and sound. While in principle, any general-purpose lossless compression algorithm can be used on any type of data, many are unable to accomplish the substantial compression on data when it is used against the type of which it is designed for. Good examples of this are audio files which cannot be compressed well with conventional text compression algorithms
Most lossless compression programs use two different kinds of algorithms: one which generates a statistical model for the input data, and another which maps the input data to bit strings using this model in such a way that probable data will produce shorter output than implausible data. Most of the times, the first algorithm is chosen over the other which is meant for the more conventional uses.
Lossy compression
Lossy compression refers to the type of data compression technique in which some data is lost in the process of compression. This is because lossy compression techniques attempt to eliminate the redundant or unnecessary information which can take up size.
Additionally, when decompressing data from lossy data compression, the retrieved data is well different from the original but suffice to say that it is still close enough to be as useful as to the original. This is best used in web application most specially in the streaming of media and applications which use the telephony technology. These methods are referred to as codecs. It is best to understand that the data compressed in lossy format can suffer losses when it is compressed and decompressed in a number of times.
The advantage which lossy methods brings in comparison with lossless methods is that a lossy method can create a much smaller and altogether compacted file than any known lossless method while still being able to achieve working ability.
These methods are most often used for compressing sound, images or videos. The compression ratio of lossy video codecs is nearly always far superior to those of the audio and still-image equivalents. Audio can be compressed at 1:10 with no noticeable loss of quality; video can be compressed immensely with little visible quality loss. Lossily compressed still images are often compressed to 1/10th their original size, as with audio, but the quality loss is more detectable, most especially upon closer review.
When a user decompresses a lossily-compressed file, the decompressed file can different as compared to the original at the bit level while still being undistinguishable to the human ear or eye for most practical purposes. Many methods focus on the idiosyncrasies of the human anatomy, taking into account, for example, that the human eye can see only certain types of light. These methods describes how sound can be highly compressed without reducing the perceived quality of the sound. These flaws caused by lossy compression that are noticeable to the human eye or ear are also known as compression artifacts
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