Indexed color and text

How the colors are encoded within the color palette map of a given indexed color image depends on the target platform. Early color techniques[ edit ] Many early personal and home computers had very limited hardware palettes that could produce a very small set of colors. In these cases, an image can encode each pixel with 4-bits, directly selecting the color to use. In most cases, however, the display hardware supports additional modes where only a subset of those colors can be used in a single image, a useful technique to save memory.

Indexed color and text

Therefore, if these fonts are not the same, this bit is simultaneously an additional code point bit. Colors are assigned in the same way as in 4-bit indexed color graphic modes see VGA color palette.

VGA modes have no need for the MDA's reverse and bright attributes because foreground and background colors can be set explicitly Underline[ edit ] The VGA hardware has the ability to enable an underline on any character that has attribute bit 0 set.

However, since this is an MDA-compatible feature, [2] the attribute bits not used by the MDA must be set to zero or the underline will not be shown.

With the default VGA palette, setting bit 0 to enable underline will also change the text colour to blue. This means text in only two colors can be underlined light blue and dark blue with the default palette. Despite all this, the underline is not normally visible in color modes, as the location of the underline defaults to a scanline below the character glyph, rendering it invisible.

Fonts[ edit ] Norton Utilities 6. All glyphs in a font are the same size, but this size can be changed. Typically glyphs are 8 dots wide and dots high, however the height can be any value up to a maximum of Each row of a glyph is coded in an 8 bit bytewith high bits to the left of the glyph and low bits to the right.

When they each point to different fonts, attribute bit 3 see above acts as a font selection bit instead of as a foreground color bit. On real VGA hardware this overrides the bit's use for color selection, but on many clones and emulators the color selection remains - meaning one font is displayed as normal intensity, and the other as high-intensity.

This error can be overcome by changing the palette registers to contain two copies of an 8-color palette. There are modes with a character box width of 9-dots e.

It is always blank, and drawn with the current background colour. These code points cover those box drawing characters which must extend all the way to the right side of the glyph box. For this reason, placing letter-like characters in code points 0xC0—0xDF should be avoided.

The box drawing characters from 0xB0 to 0xBF are not extended as they do not point to the right and so do not require extending. Mouse cursor in Impulse Tracker. The shape of the cursor is restricted to a rectangle the full width of the character box, and filled with the foreground color of the character at the cursor's current location.

Its height and position may be arbitrary within a character box. A mouse cursor in TUI when implemented is not usually the same thing as a hardware cursor, but a moving rectangle with altered background or a special glyph.

Some text-based interfaces, such as that of Impulse Trackerwent to even greater lengths to provide a smoother and more graphic-looking mouse cursor. This was done by constantly re-generating character glyphs in real-time according to the cursor's on-screen position and the underlying characters.

Indexed color and text

The latter method is considerably faster, and allows quick reading of the text buffer, for which reason it is preferred for advanced TUI programs.

The VGA text buffer is located at physical memory address 0xB Since this is usually used by bit x86 processes operating in real-mode, it is the first half of memory segment 0xB The text buffer data can be read and written, and bitwise operations can be applied.

A part of text buffer memory above the scope of the current mode is accessible, but is not shown. The same physical addresses are used in protected mode.

Applications may either have this part of memory mapped to their address space or access it via the operating system.When converting to indexed color, Photoshop builds a color lookup table (CLUT), which stores and indexes the colors in the image.

If a color in the original image does not appear in the table, the program chooses the closest one or uses dithering to simulate the color using available colors.

He also has a similar Font Color Chart (text background), and Color Chart (page background) a slider to change cell background color. (Charts and sliders each have colors) Works only in Internet Explorer, but is one of the easiest to use.

The Colors text box controls only how the indexed color table is created. Adobe Photoshop still treats the image as an 8‑bit, ‑color image. Color Inclusion And Transparency. The Color Table command lets you make changes to the color table of an indexed-color image.

These customization features are particularly useful with pseudocolor images—images displaying variations in gray levels with color rather than shades of gray, often used in scientific and medical.

This is an indexed listing of The Phobia List. Many thanks to Robert Haining for his work in compiling the list in this order. Please don't ask me about curing phobias because I know little about them. In digital photography. and imaging, indexed color is the term used to describe reduced color mapping of 8-bit or less..

This is done to reduce images to their smallest size and these images are most commonly used on Web pages as they are small and quick to load.

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