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What is Bitmapped Graphics?
A bitmapped graphic refers to a digital image in which each pixel of the image is characterized by a fixed number of bits. These pixels are arranged in the form of a grid.
From a technical point of view, it refers to a two-dimensional arrangement of pixels or dots, where the total number of these dots in the image is referred to as its resolution.
- A bitmap graphic is made up of rows of pixels of different colors that together creates an image.
- The images are usually stored as binary.
- The bit depth determines the number of colors needed for a bitmapped graphic.
- A bitmapped graphic is best to use for photographic images.
- A bitmapped graphic cannot be scaled because, when done, it will lose its quality and display a blurred image.
Understanding Bitmapped Graphics
A bitmapped graphic is the collection of small dots or pixels, a short of picture element. Ideally, it is one of the two elementary architectures of all digital images, the other being vector graphics.
A bitmapped graphic is also known by different names, such as:
- A raster graphic
- A bitmap image
Ideally, the images that you see on most of the screens are bitmapped images. These screens can be any of the following:
- A Cathode-Ray Tube or CRT monitor
- A Liquid Crystal Display or LCD
- An Organic Light Emitting Diode or OLED screen
- A plasma screen
This is because all these screens are typically bitmapped-graphics displays. When you enlarge the image displayed on any of these screens, you will see that it is made up of lots of such tiny dots.
Even the images captured by digital cameras, camcorders and scanners are bitmapped graphics, just as those created in the paint programs.
The number of colors in a bitmapped graphic is typically determined by the bit depth. This depth denotes the number of bits needed to store a single pixel on an image.
Normally, the number of colors available varies according to the bit depth. For example:
- 8 bits per pixel will offer 256 or 28 colors.
- 16 bits per pixel will offer 65,536 or 216 colors.
- 24 bits per pixel will offer 16,777,216 or 224 colors.
Since the bitmapped images are typically stored in a bitmap file, it is essential to compress it or reduce the size of the file. This will offer two significant benefits, such as:
- It will make it easier to store, needing less memory space.
- It will allow transferring the file quickly across a network.
On a bitmapped graphic, there are different types of compression methods that can be used, depending on the specific format of the file used for it. However, the two compression methods that are most commonly followed are:
- RLE or Run Length Encoding – This method is very useful to store bitmapped graphics files if a block of pixels in the set has the same color.
- LZW or Lempel, Ziv, Welch – This method is useful for bitmapped graphics with repeated patterns to store them in an index look-up table as an arrangement of pixels.
It is not easy to scale a bitmapped graphic. You cannot simply scale it up or down due to the following reasons:
- When you scale up a bitmapped graphic, the pixels must be interpolated. This results in a blurry image.
- When you scale it down, on the other hand, the pixels will be resampled. This will, in turn, result in the loss of data of the image.
How are Bitmapped Graphics Stored?
When you zoom in on a bitmapped image, you will see that it is stored as individual squares, where each square is a pixel. Ideally, each pixel or square is stored in a 2D array, and each of them can be edited separately.
These bitmapped images are stored in different graphics formats, just as bitmaps, which include:
- JPEG, or Joint Photographic Experts Group
- GIF, or Graphics Interchange Format
- BMP, or Bitmap Image File
- TIFF, or Tag Image File Format
The bitmapped graphics can be either black and white or a colored graphic.
If it is a black and white graphic, the black pixels will be represented by and stored as 1 and the whites as 0.
Each of these pixels, usually irrespective of the total number of pixels in an image, will be stored by using only one bit.
On the other hand, if the bitmapped graphic is colored, each pixel will typically need more than a single bit to be stored, along with the other data about the details of the image and its color.
This means that the file size is larger in the case of a colored bitmapped graphics because the more bits are allocated, the larger will be the size of the file to hold them.
What are the Characteristics of Bitmap Graphics?
Typically, the bitmapped graphics are characterized by their number of pixels and color depth.
They are also compressed. However, these images are not scalable or resolution independent.
How are Bitmapped Graphics Represented?
A bitmapped graphic is typically represented in a grid arrangement made up of pixels.
A bitmapped graphic is a basic architecture of digital images which is easy to use but is not scalable or independent of resolution.
The compressed size of the files of bitmapped graphics makes it easy to store them and transfer them quickly from one location to another across a network of systems or over the internet.