High Colour graphics

[Andrew]

How can I convert a mode 16 (8 bits per pixel) or a mode 32 image to mode 33?
Both modes are 16 bits/pixel, but the actual value of the colour is different.

[pjw]

I think you wrote somewhere that youd downloaded and studied all my code from Knoware. If that is the case you will have a toolkit called CV2NAT, which may do all you require. There are other toolkits too you may find useful: MBLK to move graphics data around, and some of the SBASIC routines to convert PICs to SPR and vice versa, as they show something of the layout of these structures, and padding and the like.

[tofro]

Just for completeness if you want to write something yourself:

I am (as always) a bit confused with mode designations. Looking into the Aurora technical guide names a MODE 16 with two pixels/byte (i.e. 16 colours), and names the 256-colour-mode MODE 256 (1 pixel/byte, with a complex calculation for the least significant bits). I have been (just like you) assuming up to now MODE 16 would be 256 colours. Maybe someone with an Aurora can clarify what is the truth.

For MODE 32 bit assignments are a bit weird (probably due to Intel byte order): (A pixel is one 16-bit word)

GGGBBBBBRRRRRGGG

(the most significant G bits are the ones at the end [G5-G3]!)

And for MODE 33 they look a bit more friendly: (A pixel is one 16-bit word)

BBBBBRRRRRGGGGGG

[BSJR]

How can I convert a mode 16 (8 bits per pixel) or a mode 32 image to mode 33?
Both modes are 16 bits/pixel, but the actual value of the colour is different.

There is also the BMP program on Dilwyn site that has translate options for BMP, SCR or PIC files to and from any QL or GD2 mode. As a Viewer it converts anything into the current native mode (4 or High Colour) on the fly.
https://dilwyn.theqlforum.com/graphics/index.html

BSJR

[pjw]

My assumption was that Andrew wanted to convert between formats on the fly, in which case CV2NAT - or some self-made routine would fit the bill. The included source code could be useful in the latter respect. In Wman2 for GD2 systems, there are already built-in routines to convert standard sprites of all modes into native GD2 sprites. One might also be able to make use of that..

If just a one-off conversion is wanted then, clearly, one of the viewers/converters such as BMP, QV or others would be better.

BSJR, I always intended to write something nice here about BMP but life got in the way and I forgot. Sorry.

[pjw]

<>
I am (as always) a bit confused with mode designations. Looking into the Aurora technical guide names a MODE 16 with two pixels/byte (i.e. 16 colours), and names the 256-colour-mode MODE 256 (1 pixel/byte, with a complex calculation for the least significant bits). I have been (just like you) assuming up to now MODE 16 would be 256 colours. Maybe someone with an Aurora can clarify what is the truth.
<>

In GD2 parlance mode 16 is 1 byte/pixel, ie 256 colours, grbgrbgx. I dont think I ever found a satisfactory conversion routine that would accurately convert between the other modes and mode 16, so I ended up using a lookup table instead. Others may have had better success.

As for the Aurora mode 16 you mention (1 byte/2 pixels) I never encountered it. Perhaps it has been superseded? These are the current official GD2 mode designations (for sprites, at least):

Code: Select all

        0       1 bit black&white
        3       1 bit palette mapped
        4       2 bit fixed gr palette
        7       2 bit palette mapped
        8       4 bit fixed irgb palette
        15      4 bit palette mapped
        16      8 bit fixed palette (equals Aurora palette)
        31      8 bit palette mapped
        32      16 bit QPC/QXL %gggbbbbbrrrrrggg format
        33      16 bit Q40 %gggggrrrrrbbbbbw format
        64      32 bit $RRGGBB00 format

[tofro]

As for the Aurora mode 16 you mention (1 byte/2 pixels) I never encountered it. Perhaps it has been superseded? These are the current official GD2 mode designations (for sprites, at least):

On second thought, I think the Aurora hardware seems to implement it, but there never weren't any drivers for it. Likely Nasta would know.

[BSJR]

As for the Aurora mode 16 you mention (1 byte/2 pixels) I never encountered it. Perhaps it has been superseded? These are the current official GD2 mode designations (for sprites, at least):

On second thought, I think the Aurora hardware seems to implement it, but there never weren't any drivers for it. Likely Nasta would know.

I assume some colour modes were proposed in '96 for Aurora that were never finalised in any drivers.
When the new GD2 standard was set in '98, the mode 16 was the same as mode 256 intended for Aurora, hence the confusion.

The GD2 Sprite modes 8 & 15 do use 1 byte for 2 pixels but like some other modes (1,3,4,7,31) they have not been seen in the wild yet. I have been experimenting with them and as Sprites they do work in SMSQ/E.

BSJR