![]() alignH similarly aligns the second bounding box to the right of the first, and its alignment values Top, Center, and Bottom controls the vertical placement of the second box. It also takes one of Left, Center, or Right values as the alignment parameter, which further aligns the second with the left edge, center, or right edge of the first. alignV takes two boxes and places the second below the first. The bounding boxes are used by the onto, alignH, and alignV alignment commands. For example, the bounding box of a piecewiseAffine curve is the smallest axis-aligned box, containing the points of the curve, and for a rectangle, it is the same as the rectangle. For this reason, text produces images of sequences of letters to be read on the screen, which are intentionally represented upside down, i.e., with the top bar in the letter 'T' being closer to the origin than its foot such that they are shown right way up on the screen.Įach tree has a bounding box, and the bounding box is set differently for each element. This is a natural coordinate system of images consisting of a table of pixels but may cause confusion when shown on the screen or in a file. Which implies that the origin is always rendered in the top left corner of an image and that the first coordinate, x, increases to the right, and the second coordinate, y, increases down. Anything outside the canvas is ignored.Ĭanvas uses a row-column coordinate system, as illustrated in the figure to the right Note that the size of the canvas is first specified at the point of rendering, and it is up to the programmer to ensure that the relevant graphics are placed on the canvas. In both cases, first tree is converted to a picture here called pict, and then a canvas of width 75 and height 150 is created and pict is rendered on it. The figure has been produced by rendering the following tree: To illustrate how this works, consider the following figure. ![]() The graphics tree structureĪ simple graphics primitive such as a rectangle or an ellipse are leaves in a tree, that is, a single rectangle is a tree with only one node. Interaction: DIKU-Canvas has an interactive mode, which reacts to the user input from the keyboard or mouse and allows the programmer to update the graphic tree and render the result to the screen.Ĭanvas is a system for combining simple graphics primitives.Animation: Sequences of graphic trees may be rendered as an animation to the screen or a file.Render: Graphic trees may be rendered to the screen or a file.Layering Shapes: Combine shapes by drawing them on top of each other, allowing for the creation of intricate designs.ĭIKU-Canvas has several rendering and interaction options:.Horizontal and Vertical Alignment: Utilize alignment functions to organize shapes horizontally or vertically, aiding in layout design.Scaling: Resize objects by a given scaling factor, either uniformly or non-uniformly. ![]() Rotation: Rotate objects around a specific point, providing the angle in degrees or radians.Translation: Translate objects across the 2D plane with user-defined x and y offsets.The primitives can be transformed and combined with: Ellipses: Create ellipses by specifying parameters that control shape and orientation.Rectangles: Utilize coordinates for position, width, and height to draw various rectangular shapes.Cubic Bezier Curves: Provide control over curve definition and complexity, facilitating the design of smooth and customizable curves.Circular Arcs: Defined by a center, radius, and angle, enabling precise circular structures.Piecewise Affine Lines: Represented as sequences of connected line segments, allowing for intricate paths and outlines. ![]() The collection of primitives serves as the foundation for complex geometric shapes: DIKU-Canvas also has an interactive mode that accepts input from the keyboard and the mouse. Graphic primitives may be transformed and combined in a tree structure, and the trees may be rendered to the screen or to file as a still image or an animation. ![]() This should result in a window with a green square in the top left corner on a black background. ![]()
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