This will be the color displayed on screen for the corresponding pixel. This color index is then passed to Denise which will look in the corresponding register which color is described. For each pixel, Agnus is able to fetch the corresponding bits in many biplanes to compute a color index. The first bit for the first pixel, the second bit to the second pixel, and so on. So instead of a chunky representation, the Amiga uses a planar representation.īitplanes are zones of memory in which one byte will contain information relevant to eight contiguous pixels.
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Using one full byte of memory to encode one of 32 indexes would be a waste of memory. 256-color indexed: īut Amiga can only display 32 colors, indexed from a palette of 4096.They use a chunky representation, meaning that one or many bytes are dedicated to describe one single pixel. The Amiga does not represent images in memory as modern machines do. The format is great to display photographies, but is a little bit cumbersome to manipulate and leads to some horizontal artifacts. Hold and Modify (HAM) is able to display 4096 colors at once. They are well suited to display pixel arts and drawings, and they are easily manipulated and animated by the machine. The standard planar modes, that can display up to 32 colors in LowRes (320x256) and 16 colors in HiRes (640x256). Thus, an Amiga cannot display a modern image as is: it will have to be converted to a suitable format beforehand. But Denise does not generates images as modern PCs do. All data manipulated by the chipset must reside in the shared Chip RAM (source)Īmiga image formats were devised around the capabilities of Denise. It can also display interlaced images of the same width but with a doubled vertical resolution. It can display progressive 320 or 640 pixel-wide and 200 (NTSC) / 256 (PAL) pixel-high screens. Denise is the video processor, our main interest here.It is also responsible for all the I/O, including driving the floppy. Paula hosts the audio capabilities of the Amiga: 4 independent 8-bit PCM channels that can be read at various rates.It is also sports a blittter, which can quickly copy blocks of data, and the Copper, a clever independent co-processor. It is responsible of controlling the memory access to the so-called CHIP-RAM from the various components of the Amiga, including the CPU. Especially concerning the graphical tasks. As gamers know, specialized hardware always beat software. The Amiga was designed around a custom chipset, now known as the OCS, which performed all the hard work delegated by the CPU. With dozen of applications such as Deluxe Paint or Lightwave taking advantage of these abilities, the reputation of the Amiga as a graphical workstation was well deserved.Ĭan we load a modern image on the Amiga and manipulate it with, for instance, Deluxe Paint? The Original Chipset This was way above the graphical abilities of the other personal computers on the market at that time.ĭefenders of the Crown. As early as 1985, an Amiga 1000 could display static images composed of 4096 colors or animate 32-color screens.
Amiga computers were renowned for their “multimedia” capabilities.
You can find an up to date table for APNG support in different browsers at.
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