Other meanings of Bitmap graphics
Computer graphics
Bitmap graphics are computer graphics represented as a rectangular grid of individually addressable pixels. Each pixel stores a color or intensity value, so the image’s detail depends on its dimensions, sampling, and encoding rather than on mathematical shapes.
Bitmap graphics represent an image by assigning data to discrete pixels arranged in rows and columns. A pixel may contain a direct color value, an index into a palette, grayscale information, or additional transparency data. This structure is also called raster graphics, in contrast to vector graphics, which describe lines, curves, and shapes mathematically.1 The width and height establish the image’s resolution; they do not alone determine its visual quality, because sharpness also depends on sampling, display size, and the original scene. A bitmap can therefore preserve intricate textures and irregular edges efficiently, while its file size generally grows with pixel count and the amount of information stored for each pixel.
Bitmap quality and behavior depend strongly on pixel encoding and file format. Color depth specifies how many bits represent each pixel: indexed images select colors from a palette, while true-color images commonly store separate red, green, and blue components. An alpha channel can add per-pixel opacity, allowing compositing over another image. Formats apply different strategies to this data. PNG supports lossless compression and transparency, making it useful for graphics with sharp edges or flat color fields.2 JPEG uses lossy compression designed for continuous-tone imagery, particularly photographs, and can introduce blocking or ringing artifacts after repeated processing.3 TIFF is a flexible format widely used in preservation and professional imaging workflows.4
Bitmap editing changes pixel values directly or applies operations across regions of the grid. Painting, retouching, filtering, cropping, and compositing all work at this level; a canvas or image editor may expose individual channels, selections, layers, and masks. Enlarging a bitmap cannot recover detail that was never sampled, so software must interpolate new pixels. Nearest-neighbor scaling preserves hard pixel boundaries, whereas bilinear or bicubic methods produce smoother results. Downsampling can discard detail and create aliasing unless the image is filtered first. Screens and printers also transform bitmap data through color management, interpolation, and device-specific sampling, meaning that a file’s nominal pixel dimensions are not a complete description of its final appearance. In web applications, the Canvas API provides direct access to image pixel data for drawing and manipulation.5
Bitmap graphics include several less obvious forms beyond ordinary photographic files. A one-bit bitmap can represent a monochrome mask rather than a visible picture, while indexed-color images can be extremely compact when a scene uses a limited palette. Transparency may be binary, as in a cutout mask, or continuous through an alpha channel. Some formats store rows in a particular order, divide data into tiles or strips, or retain multiple pages and high-bit-depth samples; these details matter in scientific imaging, scanning, cartography, and archival preservation. The GIF format, for example, is limited to an indexed palette per image but can combine frames into simple animations.6 Bitmap data also underlies image sensors, texture maps in three-dimensional graphics, and many digital documents, even when users encounter only a compressed file or rendered page.
Bitmap and raster are commonly used as near-synonyms here; the article concerns grid-based computer images, not unrelated uses of the word bitmap.
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