Image file formats

Image file formats are standardized means of organizing and storing digital images. Image files are composed of digital data in one of these formats that can be rasterized for use on a computer display or printer. An image file format may store data in uncompressed, compressed, or vector formats. Once rasterized, an image becomes a grid of pixels, each of which has a number of bits to designate its color equal to the color depth of the device displaying it.

Image file sizes

The size of raster image files is positively correlated with the resolution and images size (number of pixels) and the color depth (bits per pixel). Images can be compressed in various ways, however. A compression algorithm stores either an exact representation or an approximation of the original image in a smaller number of bytes that can be expanded back to its uncompressed form with a corresponding decompression algorithm. Images with the same number of pixels and color depth can have very different compressed file size. Considering exactly the same compression, number of pixels, and color depth for two images, different graphical complexity of the original images may also result in very different file sizes after compression due to the nature of compression algorithms. With some compression formats, images that are less complex may result in smaller compressed file sizes. This characteristic sometimes results in a smaller file size for some lossless formats than lossy formats. For example, graphically simple images (i.e. images with large continuous regions like line art or animation sequences) may be losslessly compressed into a GIF or PNG format and result in a smaller file size than a lossy JPEG format.

Arm Image Format

In computer programming, the Arm Image Format (AIF) is an object file format used primarily for software intended to run on ARM microprocessors. It was introduced by Acorn Computers for use with their Archimedes computer. It can optionally facilitate debugging, including under operating systems running on other processor architectures.

Format

The file can be either executable or non-executable and is loaded at 0x8000 unless otherwise specified. Executable files can relocate themselves if necessary and non-executable files are prepared for execution by an image loader. An extended AIF is a type of non-executable which includes information to enable the placement of code and data within specific areas of memory.

The file includes a header and separate areas of read-only and read-write code/data. It can optionally include data for debugging and the code (with list) for self-relocation.

AIF header

The header includes information about self-relocation, entry point, exit instruction, area sizes and locations, debug type, addressing mode and memory placement (in the case of the extended file).