Please help with scaled sprite put

I have a rgba buffer I need to put to screen and have the correct colours on my ARMX6. I wonder if a:) WIll it work with scaled put? and b) how do I use it.?

All atempts so far have failed.

Are you trying OS_SpriteOp 52 (Paint sprite scaled)?

Do you only have the array of pixels? If so, you would need to put a sprite header on the front to use that call.

I have a sprite with rgb data in it. It is Colour trans I have problems with.

I have tried to to read the docs … I can’t find info how to translate from rgb to bgr..
Is it possible?

I am using cairo to render to the spritedata , and cairo doesnt have bgr modes on surfaces (afaik).

OK. I implemented byte switching , and that works , takes some time .

I don’t know what Cairo is, but have you checked that the sprite type information is correctly identifying the sprite as RGB rather than the usual BGR?

It should have a RISC OS 5 style mode sprite word:
https://www.riscosopen.org/wiki/documentation/show/Sprite%20Mode%20Word

Where the mode flag bits 12-15 describe its colour format:
https://www.riscosopen.org/wiki/documentation/show/Mode%20Flags

Rummaging around SpriteExtend (which is really weird!) it does look like it ought to “just work”.

I have been tracing the wiki , but I havent found a clear path!

From my own WimpLib:

\
const _kernel_oserror* Desktop_PlotSprite(const CSpriteHdr* pSprite, CPoint pt, const CSpriteFactors* pfactors)
{
 const _kernel_oserror* err;
 CSpriteFactors  scale;
 int mode;
 int palette;
 int log2bpp;
 int ptable[256];

 if (!pSprite) return NULL;

 // Get wimp scale factors and translation table from Wimp_ReadPixTrans
 err = _swix(Wimp_ReadPixTrans, _INR(0,2)|_IN(6)|_IN(7), 0x200, 0x100, pSprite, &scale, ptable);
 if (err) return err;

 // Read palette info
 err = _swix(OS_SpriteOp, _INR(0,3)|_OUTR(4,5), 0x200 + 37, 0x100, pSprite, -1, &palette, &mode);
 if (err) return err;

 // Call OS_ReadModeVariable for log2 number of bits per pixel
 err = _swix(OS_ReadModeVariable, _INR(0,1)|_OUT(2), mode, 9, &log2bpp);

 // Has a palette or has more than 16 colours ?
 if (palette
 ||  (log2bpp > 2))
 {
  // Get translation table from ColourTrans_SelectTable
  // Do not use bit 4 (0x10), OS_SpriteOp does not know about multibyte colors
  err = _swix(ColourTrans_SelectTable, _INR(0,5), 0x100, pSprite, -1, -1, ptable, 0x01);
 }

 // Update scale factors
 if (pfactors)
 {
  scale.xmag *= pfactors->xmag;
  scale.ymag *= pfactors->ymag;
  scale.xdiv *= pfactors->xdiv;
  scale.ydiv *= pfactors->ydiv;
 }

 // Plot sprite
 err = _swix(OS_SpriteOp, _INR(0,7), 0x200 + 52, 0x100, pSprite, pt.x, pt.y, 0x18, &scale, ptable);

 return err;
}

Another example:

https://gitlab.riscosopen.org/RiscOS/Sources/Video/Render/SprExtend/blob/master/Test/c/bigtest#L807

This is for a single-tasking test app, so it doesn’t use Wimp_ReadPixTrans (which I think is only needed in André’s code because the Wimp uses a different default palette for low-colour sprites/modes than the rest of the OS uses)

Also, both of the examples are naughty and don’t read the required size of the translation table (by making an initial call to ColourTrans_SelectTable / ColourTrans_GenerateTable with R4=0).

More info here

// Do not use bit 4 (0×10), OS_SpriteOp does not know about multibyte colors

You need to set bit 5 of the OS_SpriteOp 52 flags. Basically bit 5 of the OS_SpriteOp flags must match bit 4 of the ColourTrans flags.

Thanks for all help. I haven’t implemented this yet, but I need to do it soon.

You need to set bit 5 of the OS_SpriteOp 52 flags. Basically bit 5 of the OS_SpriteOp flags must match bit 4 of the ColourTrans flags.

Unfortunately bit 5 of OS_SpriteOp 52 was not documented in the PRM Volume5, which left me puzzled as to the purpose of the ColourTrans flag if OS_SpriteOp could not make use of the output.