A printer matching 200 pixels per inch (PPI) screen resolution my have to have a resolution exceeding 1000 dots per inch (DPI) to represent it on the printed page. Modern printers have much higher resolutions to match the individual pixels in the raster image. Together these represent the colour of one pixel. To get the colour right in a colour dot on a page, three (or more) ink colours are used. It should be remembered that in printing, the resolution of an individual dot is not the same as an individual pixel. The quality of some printers allows printing resolutions into the thousands of Dots per Inch. Likewise, modern printers can print at high resolution too. This makes the images look much sharper and smooth edged. Modern high resolution screens can display raster images in very high quality because the individual pixels are smaller and closer together. The resolution of a raster image is also dependent on the hardware it is displayed on or the printer that prints the image. You have to experiment with different images to see how they work in reduction. To what extent the damage affects the viability of the raster image depends on the image itself and the degree of size reduction. With a little sharpening to preserve edges, the image can be reduced by large percentages before the quality is badly affected. Reductions in size of a raster image involve dumping of the pixels between colours in a way that tends to preserve the colour gradient. The eyes are better at seeing things that are smaller and recognizing them even with reduced detail. So as the size increases the image begins to blotch and form artifacts in the image that are not seen in the real world.Ī raster image can be reduced in size with less apparent damage. A computer cannot add new data to make an image look real. As the image gets bigger this does not fool the eye. However, these rely on putting new near-colour pixels around existing ones. Some image editors have some good tricks available to mimic increase in size. Attempts to change the size of the image will cause apparent damage to the visible quality of the image. The raster image cannot change its scale. These models describe each of the colours, how they graduate between colours, and how many colours are included in the model. Common colour models include RGB, CMYK and some proprietary ones branded by companies. In photography colours are represented by a colour model. Colours in a raster image are themselves represented in a number of ways. An accompanying number indicates the the Colour Depth. Typically a raster image is measured by the number of pixels wide by the number of pixels high. The more a file is compressed the more the quality deteriorates. While the latter are easier to edit the files are too large to use on the It also affects the quality. This is to enable a faster transfer of the data for use over computer networks and the World Wide Web (This is in contrast to the RAW images where all the data is in the file. The *.jpg, *.gif and *.PNG formats are created by a process that compresses the amount of data found in the file. They may be found as *.jpg, *.gif or *.PNG or any of a wide range of other formats. In most cases the images are picture formats like photographs. Raster image formats for storageĪ raster image, also known as a bitmap, can be stored in a variety of formats. The full raster image is the composite of all the pixels put together as the image showing on your screen. Together the pixels merge before your eyes into one coherent whole. When the sensor data from all the photosites are translated into an image on your screen, each photosite becomes an individual pixel in the image.Įach of the tiny pixels in a raster image are too small to see individually. Raster image (also called a bitmap image)Ī picture created in a camera comes from an array of tiny sensors ( photosites) on the digital image sensor.
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