Award BIOS logo
(→Version 2) |
(→Version 2) |
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| Line 43: | Line 43: | ||
| ''width'' × ''height'' bytes | | ''width'' × ''height'' bytes | ||
| The image data; a series of rows of pixels. | | The image data; a series of rows of pixels. | ||
| − | * In the 4-bit variant, each row of pixels is stored as four bitmaps, each storing one bit of the pixel values, starting with the bitmap for the least significant bit. Within each bitmap, pixels are stored left-to-right, and the most significant bit is the leftmost one. | + | * In the 4-bit variant, each row of pixels is stored as four "plane" bitmaps, each storing one bit of the pixel values, starting with the bitmap for the least significant bit. Within each bitmap, pixels are stored left-to-right, and the most significant bit is the leftmost one. If the image width is not a multiple of 8, each "plane" bitmap is separately padded to a multiple of 8 bits. |
* In the 8-bit variant, this is simply an array of pixel values, stored row-by-row, left-to-right. | * In the 8-bit variant, this is simply an array of pixel values, stored row-by-row, left-to-right. | ||
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Revision as of 18:24, 20 March 2015
Award BIOS logo (also known as EPA or AWBM) is a family of image formats associated with Award BIOS firmware. These formats are used by those who wish to change the image shown on the boot screen of certain computers. The default image is usually an "Energy Star" logo.
Contents |
Format
There are at least two main versions of the format, sometimes called "version 1" and "version 2". Additionally, different versions of the BIOS have different restrictions on the size of the image, etc. There is evidence that different BIOS versions may even render the same file differently.
Version 1
Version 1 images are rendered in text mode, by customizing the character graphics. Consequently, each 8×14 cell of pixels can only use two different colors.
There is no identifying signature, but most files begin with 0x11 0x06 or 0x11 0x09, based on the usual dimensions of the image in cells.
There are usually two images in the file, the second being the small blue Award logo that also appears on the boot screen.
Version 2
Version 2 files begin with a signature of "AWBM". This is a more typical kind of image format, not based on character graphics. It appears in two variants: "semi-planar 4-bit" and "packed 8-bit".
All values are little-endian.
| Name | Length and type | Description | |
|---|---|---|---|
| 4-bit variant | 8-bit variant | ||
| magic | 4 bytes | Always equal to 'A' 'W' 'B' 'M' (i.e. 41 57 42 4d)
| |
| width | uint16_t | Image width and height in pixels. Common image dimensions include 136x84, 136x126 and 640x480. | |
| height | uint16_t | ||
| data | width × height / 2 bytes | width × height bytes | The image data; a series of rows of pixels.
|
| palmagic | 4 bytes | Always equal to 'R' 'G' 'B' ' ' (i.e. 52 47 42 20).
| |
| paldata | 16 × 3 bytes | 256 × 3 bytes | EGA palette data: an array of triplets of bytes in range 0..63. In the 4-bit variant of the format, the basic colour intensities are stored in blue-green-red order, while in the 8-bit variant they are stored as red-green-blue. |
