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GRAPHIC FORMATS AND TERMS
Bitmap (raster image)
A bitmap (raster image, when converted from vector image) is a graphics image composed of small dots (pixels).
These dots can be simple on-or-off bits (a monochrome bitmap), or represent colors. Windows supports four levels
of raster images:
- monochrome (1 bit per pixel),
- 16-color (4 bits per pixel),
- 256-color (8 bits per color),
- 16 million color (24 bits per pixel).
Raster images do not generally scale to larger sizes very well; the dots become squares or rectangles and the image
appears grainy. Also, raster images use lots of disk space and memory. However, they display faster than metafile
(vector) images and can show much more true-to-life detail. Scanned images, such as Compuserve GIF files, are raster
images.
Video cards can be purchased as a separate upgrade available in all major retail stores, or as an integrated
component in today's new AGP and PCI systems. Video cards will offer more colours to be displayed and they accelerate
the display performance as well as the quality of the images.
Pixel
A pixel is a dot in a raster image, or bitmap.
Depending on the color resolution, a pixel takes from 1 to 24 bits to represent in memory and on disk. Therefore,
an uncompressed bitmap which is 100 pixels wide by 100 pixels high can require from 10,000 to 240,000 bits (1250
to 30,000 bytes).
GRAPHIC FORMATS
Popular graphics file formats:
BMP file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| No |
Yes |
Yes |
Yes |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
No |
No |
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CPT file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Always Saved |
Yes |
Yes |
Yes |
| TransparentColor |
Compression |
VariableCompression |
|
| Yes |
No |
No |
CPT
The filename extension associated the native file format of Corel PHOTO-PAINT. .CPTs are bitmapped graphics that
represent shapes as pixels arranged to form an image. CorelDRAW can import and export files in .CPT format, including
files that contain color and grayscale information. In Corel PHOTO-PAINT, masks, floating objects, and lenses are
saved with the image when you save in the .CPT format.
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FPX file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Always Saved |
Yes |
No |
No |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
No |
No |
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GIF file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| No |
No |
Yes |
No |
| TransparentColor |
Compression |
VariableCompression |
|
| Yes |
No |
No |
GIF
Supports 8-bit indexed color for a display of up to 256 colors. The GIF format is a good choice for compressing
solid areas of color while preserving sharp detail, such as that in line art, logos, or illustrations with type.
When you export to the GIF format, ImageStyler generates an adaptive indexed color table that contains the colors
most commonly used in the image. ImageStyler then shifts the colors toward the Web-safe palette—the set of colors
used by Web browsers when displaying images on an 8-bit color display. If your composition is primarily composed
of Web-safe colors, this shift toward the Web palette helps ensure that your exported GIF image's color table is
predominantly comprised of Web-safe colors.
The GIF format uses a lossless compression method in which no data is discarded during compression. However,
since GIF images can use a maximum of 256 colors and ImageStyler compositions can be made up of millions of colors,
you may see degraded image quality when saving to the GIF format. ImageStyler creates an interlaced GIF image,
in which a low-resolution version of the image appears in a Web browser while the full image is downloading.
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JPG file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| No |
Yes |
No |
No |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
Yes |
Yes |
JPEG, Joint Photographics Experts Group
JPEG file format is nn international bitmap file format standard for image compression that offers compression
with almost no losses at ratios up to 20 to 1. Also known as JFIF (for JPEG File Interchange Format). JPEG is supported
by all platforms up to 24-bit color. Maximum image size is 64,000 pixels by 64,000 pixels. Supports JPEG compression.
Used as a storage and exchange format for files containing data that has been compressed with JPEG.
The JPEG file format was developed as a compression scheme designed specifically for computer images. JPEG supports
up to 32-bit color (4.2 billion colors) and is, therefore, an excellent option for photographs, image maps, and
scanned color images.
Designed for use with photographic images, and other continuous-tone images. JPEG uses 24-bit color, and preserves
the broad range and subtle variations in brightness and hue found in photographs. The JPEG format uses a lossy
compression method, in which data is discarded during compression. The JPEG compression method can degrade sharp
detail in some images, such as images containing type or line art. You specify the amount of compression to be
applied by choosing a quality setting. A higher quality setting results in less data being discarded and a larger
file size.
Note: Data is discarded from a JPEG image each time you export a JPEG file. You should always save JPEG
files from the original composition if possible, rather than reimporting and exporting the image multiple times.
JPEG files use lossy compression, which means that the image loses information while continuing to provide
high-quality images with a high level of compression. You can choose the image qualitythe higher the image quality,
the larger the file size. Some Web browsers support progressive JPEG images. Progressive images appear on screen
gradually so that you can see portions of an image before it finishes loading.
Lossless
The maintenance of image quality of an image that has been compressed and decompressed. The process of compressing
and decompressing often degrades image quality. A lossless image is one in which the image quality of a decompressed
file appears nearly identical to the original.
Interlacing
A method that lets you display an image onscreen, but at a low, blocky resolution, as soon as the image appears
onscreen. As the image data loads, the image quality improves.
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MPEG ( Motion Pictures Experts Group )
A popular codec (compression and decompression algorithm) for squeezing full-screen, VHS-quality digital video
into a small data stream so that it can be played from a CD-ROM drive. MPEG is an intense and thorough way of compressing
data. MPEG allows for VHS-quality (that is, 640x480, 30 frames-per-second) digital video playback at very low data
rates. A double-speed CD-ROM is sufficient for playback of this quality of video.
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PNG file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Yes |
Yes |
Yes |
No |
| TransparentColor |
Compression |
VariableCompression |
|
| Yes |
No |
No |
PNG file format
The PNG (Portable Network Graphics format is intended to provide a portable, legally unencumbered, well compressed,
well-specified standard for lossless bitmapped image files. Although the initial motivation for developing PNG
was to replace the GIF format, the design provides some useful new features not available in GIF, with minimal
cost to developers. Some features not availble in GIF format are:
-Truecolor images (up to 48 bits per pixel),
-Grayscale images of up to 16 bits per pixel,
-Full alpha channel(general transparency masks,
-Gamma brightness indication,
-better detection of file corruption
-faster load time in progressive display mode.
PNG-images have an extra ALPHA-channel which retains the layer information of the original files.
PNG format information
PNG is the Portable Network Graphics file format. Although many Web browsers cannot yet display PNG files without
a special plug-in, this file type is rapidly growing in popularity on the Web. Because .png files are lossless,
there is no image degradation when the image is compressed. Image Composer saves .png files as a single sprite
in true color or with a custom color palette, such as Gray Ramp, Web (Dithered), or Web (Solid).
Keep transparency
You can save a sprite with or without the alpha channel. When the Keep transparency check box selected, Image
Composer saves the sprite as an RGBA image. Keep transparency is selected as the default setting. Stores images
with the Alpha, or transparent, channel included. The image is then an RGBA (Red, Green, Blue, Alpha) image.
Transparent color
You can designate a palette color as the transparent color of the composition or selection to be saved in .gif
or .png files. If you select this check box, you can assign a color for the transparent color by clicking the color
chip. To determine which pixels are changed to the designated transparent color, move the Threshold slider or enter
a value between 0 and 255 in the Threshold box. For more information, see Adjusting the threshold of a .gif or
.png file.
Properties for each particular option you choose appear to the right of the Color format list.
PNG-Indexed
Also known as PNG-8, supports 8-bit indexed color. Like the GIF format, PNG-Indexed compresses solid areas of color
while preserving sharp detail, such as that in line art, logos, or illustrations with type. The PNG-Indexed format
uses a lossless compression method, in which no data is discarded. ImageStyler use the composition's alpha channel
or active matte information to export PNG-Indexed files with a single level of transparency. PNG-Indexed is supported
directly by Internet Explorer 4.0 and later, and by Internet Explorer 2.0 or later and Netscape Navigator 2.0 or
later using a plug-in.
PNG-Truecolor
Also called PNG-24, supports 24-bit color. Like the JPEG format, PNG-Truecolor preserves the broad color and tonal
range of photographic images. Unlike JPEG, PNG-Truecolor uses a lossless compression method, in which no data is
discarded. ImageStyler exports PNG-Truecolor files with a single level of transparency. PNG-Truecolor is supported
directly by Internet Explorer 4.0 and later, and by Internet Explorer 2.0 or later and Netscape Navigator 2.0 or
later using a plug-in.
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PSD file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Always Saved |
Yes |
No |
No |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
No |
No |
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TGA file format
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Yes |
Yes |
No |
Yes |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
Yes |
No |
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TIFF ( *.tif ) is a multi-page format.
| Alpha |
TrueColor |
PaletteColor |
Alpha as Color |
| Yes |
Yes |
No |
Yes |
| TransparentColor |
Compression |
VariableCompression |
|
| No |
Yes |
No |
TIF: Tagged Image File Format
The Tagged Image Format was developed by several companies, including Aldus, to be the be-all and end-all of image
file formats. Because of its scope and extensibility, it is an extremely complex format which no single product
can support completely. TIFF is a clear example of the danger of design by committee. The known TIFF formats not
yet handled by ThumbsCD are:
- Images in YCbCr (YUV) or proprietary color formats.
- Multiple-image TIFFs (only the first image is accessed)
- JPEG-in-TIFF (JTIF) (let's take two very complex file formats and cram them together).
The following compression methods and special-interest formats are supported:
- Tiled TIFFs
- CCITT RLE, Group 3, and Group 4 Fax compresions
- Packbits, Thunderscan and Next compresion
- LZW compression
- Motorola (MM) format
ThumbsCD writes uncompressed TIFFs, or compressed via CCITT Group 3 or 4 FAX, Packbits, or LZW.
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WMF, MF: Windows Metafile
The Windows Metafile format is the standard Windows format for storing vector (metafile) information. It's quite
powerful, as anything that can be drawn on the screen or printed on a printer can be stored in a metafile. It does,
however, lack several rather rudimentary graphics primitives, such as Bezier curves and non-orthogonal ellipses.
Metafile (vector image)
A metafile is a stored sequence of drawing commands which the computer can repeat to generate an image. Metafiles
can contain simple drawing commands (such as line, rectangle, circle, arc, polygon); they may also contain commands
to set colors, fill areas, display text, and even include bitmaps. Thus, metafiles are much more flexible than
bitmaps, but they are more difficult for programmers to support and slower to display.
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