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Cartograms
Published in Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard, Thematic Cartography and Geovisualization, 2022
Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard
The term alpha in value-by-alpha map comes from the usage of the alpha channel in computer graphics. In an interactive graphical display, individual picture elements (pixels) are composed of red, green, and blue primary colors. A separate alpha channel is used to determine the level of transparency (or alternatively opacity) of each pixel. In Figure 20.16, the values of the alpha channel would be varied as a function of the population values. Assuming that alpha values range from 0 to 100 percent, the background would be depicted with an alpha of 0 percent (completely opaque), the highest population class would be depicted with an alpha of 100 percent (completely transparent), and intermediate classes would have values between 0 and 100 percent (Roth et al. suggested alpha values of 10, 30, 55, and 80 percent for the intermediate classes).21
The World Wide Web
Published in David Austerberry, The Technology of Video and Audio Streaming, 2013
GIF is a copyright of CompuServe (AOL) and distributed under a royalty-free license for general use across the web. PNG was developed as an alternative open format, with additional features. It had limited support from the earlier browsers, so had a slow acceptance by web designers. It uses lossless compression, and can encode grayscale or color images, up to 24 bits per pixel. It carries an alpha channel to define the transparency.
Interact with Me
Published in Chris Jackson, Flash Cinematic Techniques, 2012
The sky and clouds artwork was saved as a JPEG file. The middle ground was saved as a PNG file. PNG files retain the transparency of the alpha channel. After being imported into Flash, the artwork was converted into a movie clip and positioned on the appropriate layer in the Timeline.
Exploring perceived openness and spaciousness: the effects of semantic and physical aspects
Published in Architectural Science Review, 2022
Alper Ünlü, Erincik Edgü, Mehmet Emin Şalgamcioğlu, Nevset Gul Canakcioglu
The assumption in this study was that the perception of spaciousness is related to the scope of vision in terms of the farthest and widest ranges that shape the volume of the space. Therefore, considering the transparency of surfaces, visual access – in other words the visible amount of sky – is a valuable quality. Dogrusoy and Tureyen (2007) noted that due to human vision, although vertical windows offer variability from ground to sky, people prefer full window walls and horizontal window openings that facilitate horizontal eye movements. They also added visual communication with the exterior, which is considered to be more important than the quality of the view. These findings supported the motivation to use the infinity index to determine the farthest distance of view; therefore, the infinity index was used at each vantage point scene to calculate the perceived spaciousness and to present the differences between spaces. However, no matter how small it was, since the amount of sky seen will produce an indefinite distance that is useless in the calculation of volume, the initial idea of limiting the distance with the farthest interior range was abandoned. Instead, the Alpha Channel (2018) filter, which is a colour component that represents the degree of transparency or opacity, was implemented in VRay. The Alpha Channel visualizations for infinity index calculations are shown in Figure 6, where the processed image is in the middle, while the original image is on the right.
Shared Gaze in Collaborative Visual Search
Published in International Journal of Human–Computer Interaction, 2019
Harri Siirtola, Oleg Špakov, Howell Istance, Kari-Jouko Räihä
Figure 5 shows how participants verbalized their search strategy, and displays a heat map of each participant’s gaze samples. The heat map fuses together all trials from trial number 49, that is, after the first three repetitions of 16 trials. It was observed that, if a search strategy emerged, it was during the four first repetitions, if ever. The heat map was constructed by dividing the screen area into pixel rectangles which were colored according to gaze sample numbers, and the alpha channel was adjusted to let colors blend. The heat maps have (hand-drawn) overlays of observed search patterns (or approximations of them). The most popular search pattern was clockwise (11), and counterclockwise (2) and S-shape (2) were also present.
Usability of value-by-alpha maps compared to area cartograms and proportional symbol maps
Published in Journal of Spatial Science, 2019
Peichao Gao, Zhilin Li, Zhe Qin
The other variable, termed the equalizing variable, is a quantitative attribute that indicates the significance of each enumeration unit, such as the number of electors of each state in Figure 1. This variable is represented by the transparency of enumeration units in a value-by-alpha map. Note that in the digital world, transparency is controlled by the alpha channel with a value range from 0 (fully transparent) to 100 per cent (fully opaque), so the values of the equalizing variable are in fact visualized by using the alpha channel, hence the term ‘value-by-alpha’. Readers at this point may recall bivariate area cartograms, where the value of the equalizing variable is visualized by changing the actual area of enumeration units and distortion is thereby introduced. It is in this sense that value-by-alpha maps can serve as a good alternative to cartograms.