Images - The Specialty of Computing PDF

Images – The specialty of Computing Vector and Bitmap Images Vector images are images that are formed using objects and their properties- these store the information needed to create an image on a screen, they work based on algorithms instead of pixels. Standard size ranges from 1000 x 10...

Images – The specialty of Computing Vector and Bitmap Images Vector images are images that are formed using objects and their properties- these store the information needed to create an image on a screen, they work based on algorithms instead of pixels. Standard size ranges from 1000 x 1000px to 4800 x 4800px. Objects are mathematically defined expressions which are the basic elements that create vector images; they have properties that influence their characteristics that include shape and size. Because vectors are images created by shapes, zooming in will not lead to pixelation. Bitmapped (or raster) images are images created by taking photos with digital cameras which will store the images as grids of pixels with each pixel representing a colour captured by the camera's sensors. They are pixel based, therefore resolution dependent- the number of pixels determine the quality of an image. It results in a factor called 'pixelation', where the square pixels of the image become more prevalent when zooming in, making the image seem blocky and blurry. Image resolution Image quality is affected by the resolution (The fineness of detail(pixel) that can be seen in an image - the higher the resolution of an image, the more detail it holds.) of the image. Image resolution is the number of pixels in a specific area of an image. In a low-resolution image, the pixels are larger and therefore, fewer are needed to fill the space. This results in images that look blocky or pixelated. An image with a high resolution has more pixels, so it looks a lot better when it is enlarged or stretched. The higher the resolution of an image, the larger its file size will be. To calculate the file size, you use the equation: Width x Height x Color Depth  How are Pixels and Bits connected? Each pixel is stored with a certain number of bits, this is known as the bit depth, this stems from the idea that the more amount of colours needed for an image, the more pixels it needs, this means that images with more color use up a lot more storage, as they need more bytes to store each pixel. This is what we call colour depth. A color can be represented with combinations from the allocated bits. Since 8 bits have 256 total combinations, 256 colors can be represented in an image with 8 bits. For instance. 2 bits will offer 4 total combinations: 01, 00, 11, 10. A color is stored in each of these combinations, meaning 4 colors can be represented with 2 bits. Each extra bit will double the range of colors. Each pixel in an image will hold a value of bits that define its colour depth. They are represented in a grid with each pixel holding and representing a colour defined by its depth. How are images detected ? Computers operate by using binary sequences of 1's and 0's. Computer uses algorithms and machine learning techniques to recognize and determine the colors and the objects. When computers represents an image, it is arrayed as a grid of pixels each filled with one color that depicts by a distinctive binary pattern. How are different colors detected ? Human eye senses different wavelengths of light. Red – Long wavelengths Green- Medium wavelengths Blue – Short wavelengths Those are represented by RGB in computers.  Images and colours RGB range: Each component can take any value between 0 (black) and 1 (white). If each component takes a value between 0 and 1, the total range of possible colors is 0 to 255. When these three numbers are added together, the resulting number represents the light's intensity. RGB lighting creates a wide variety of colors that range from warm orange to cool blue. RGB lighting technology is often used in RGB light-emitting diode strips. RGB (red, green and blue) refers to a system representing the colors used on a digital display screen. Red, green and blue can be combined in various proportions to obtain any color in the visible spectrum. The RGB model uses 8 bits each -- from 0 to 23 -- for red, green and blue colors. Each color also has values ranging from 0 to 255. Better image quality- relation to bits Image resolution refers to the clarity of an image as it appears on a screen- It's expressed as the number of pixels that an image contains per inch, e.g. 200 ppi (pixels per inch). Bitrate is the rate where information is carried in bits (bits per second), often seen as the amount of information per second The higher the bitrate, the more data will be passed to re-create images Colour depth can affect image quality- an image with a small number of bits can use less colours than an image with more bits, it results in poor quality because more colours Types of Image Formats Images can be saved in different formats, from more of the known ones like JPEG and PNG, to others that include BMP, GIP , TIF. JPEG is a type of format that also allows for lossy compression, lossy compression allows for data to be removed from an image with a viewable difference between them. It does mean that any compression that happens, means that the data gets permanently deleted, therefore is irreversible. But works as the best compression as it removes the most. JPEG files are useful for sharing images, as they use the least amount of data. PNG is an uncompressed format, called lossless, where the image stays the same, it may remove data such as metadata but will keep the image looking the same, as well as having reversable change having been played out. TIFF, GIF and BMP are all examples of Raster Images,  Key Fact: Metadata is data Meta data- Matthew about data Files contain extra data called metadata. Administrative metadata: the information Metadata includes data about the file itself about the history of an object i.e who such as: File type, date created and author. An used to own it and what can be down image file also includes metadata about the with it such as rights, permissions and image itself such as the height and width of license. This is helpful for people the image the resolution, the colour depth and managing and taking care of an object the time of when the picture was taken and locations. Meta can be broken down into 2 forms: Structural and Administrative. Structural metadata Information on how an object should be categorised so that it fits in a larger system with other objects. Structural metadata establishes a relationship with other files so they can be organised How do digital cameras use analogue to digital converters-Matthew Analogue signals must be converted first before becoming digital. This is done by a process known as digitization. This allows for analogue data to be stored by many digital devices. Digitization can be broken down into 2 key stages: sampling and quantization. Sampling involves taking in frequent measurements in regular intervals of the analogue signal. Quantisation is used to map out the measured samples to a series/set digital values. This is done by a ADC (shown below)