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The eye is more sensitive to changes in the orange-blue (I) range than in the purple-green range (Q)—therefore less bandwidth is required for Q than for I. Broadcast NTSC limits I to 1.3 MHz and Q to 0.4 MHz. I and Q are frequency interleaved into the 4 MHz Y signal, which keeps the bandwidth of the overall signal down to 4.2 MHz.
Here is an example of color channel splitting of a full RGB color image. The column at left shows the isolated color channels in natural colors, while at right there are their grayscale equivalences: Composition of RGB from three grayscale images. The reverse is also possible: to build a full-color image from their separate grayscale channels.
In the RGB model, hues are represented by specifying one color as full intensity (255), a second color with a variable intensity, and the third color with no intensity (0). The following provides some examples using red as the full-intensity and green as the partial-intensity colors; blue is always zero:
The unambiguous way to refer to these formats is via the FourCC code. [17] To convert from RGB to YUV or back, it is simplest to use RGB888 and 4:4:4. For 4:1:1, 4:2:2 and 4:2:0, the bytes need to be converted to 4:4:4 first.
The 3-3-2 bit RGB use 3 bits for each of the red and green color components, and 2 bits for the blue component, due to the human eyes having lesser sensitivity to blue. This results in an 8×8×4 = 256-color palette as follows: This palette is used by: The MSX2 series of personal computers; Palette 4 of the IBM PGC; Extended Graphics Array (XGA)
RGB channels roughly follow the color receptors in the human eye, and are used in computer displays and image scanners. If the RGB image is 24-bit (the industry standard as of 2005), each channel has 8 bits, for red, green, and blue—in other words, the image is composed of three images (one for each channel), where each image can store ...
RGB is a device-dependent color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual red, green, and blue levels vary from manufacturer to manufacturer, or even in the same device over time.
ImageMagick, invoked from the command line as magick, is a free and open-source [3] cross-platform software suite for displaying, creating, converting, modifying, and editing raster images. ImageMagick was created by John Cristy in 1987, it can read and write over 200 image file formats. It is widely used in open-source applications.