GitLab

When clear, r2 and r3 are preserved per PRM documentation.
Also BIC'd out bits 7-10 of r0 on return so they can be reused in future, previous version would always have returned &C in those bits.

Version 1.36. Tagged as 'SprExtend-1_36'

Setting bit 1 of r0 in JPEG_FileInfo and JPEG_Info will now return the SOF type of the JPEG in question in bits 3-6 of the info flags in r0 on exit.
Took this opportunity to refactor find_image_dims to take a structure pointer rather than lots of individual pointers (CFSI-JPEG ammended to match). Untangled the return codes a bit so it is only necessary to inspect r0 on exit from C to determine the outcome. Values of 1 & 2 are translated in the assembler code into more specific error messages than just "Incomplete or corrupt JPEG".
Fix bug where unknown density marker would leave the file open in JPEG_FileInfo.
Don't bother ADRL'ing r1 for error messages that don't have a %0 in them.
Added all the input & output flag definitions to the exported header file so other callers can use them too.
More functionality, fewer bugs, about 200 bytes smaller too.

Version 1.35. Tagged as 'SprExtend-1_35'

In find_image_dims() the while loop is only exited when SOF0 or SOF1 (the two supported ones) is encountered, the other 14 possible combinations got stuck in a loop because OS_GBPB doesn't return an error at EOF.
Check added for OS_GBPB returning nothing, plus an exit when a SOS or EOI tag is hit for the memory only check (it's not possible to know where the end truly is in that case.
jcconv: warning supressed.
SWIs: comment corrected.
Tested with a bogus SOF, now gives an error message instead.

Version 1.34. Tagged as 'SprExtend-1_34'

There's no need for the C code to know which pool of memory it's using, so simplify it to just use malloc() and realloc(), the assembler implementation can then select whether the RMA or a dynamic area is in use based on the 'dynamicarea' switch.
Be more careful about area_number when it is zero, since we use that to denote the area is not yet set up but area zero is a valid dynamic area number!
Trim out some unused workspace.
Variable ccompiler_errptr had '# 0' bytes assigned, resulting in writes off the end of the workspace.
Retire DUMPVAL[N]() macro.
Remove M_SOF9 as one of the SOF markers accepted - this is allocated to arithmetic JPEGs which aren't currently supported.
Save a few words by: changing arbitrary constants (eg. safety margins) to be a power of two so they can be register immediates; numerous loads and stores of R12 relative variables changed to not use ADRL; jpeg_fetchroutine similarly simplified.

Version 1.33. Tagged as 'SprExtend-1_33'

The exit_c function was repeatedly being called with the line number argument and error code the wrong way round and since only bits 0-2 of the error code are inspected on exit any fatal exits from the ported JPEG library code would either report the wrong error or fail silently (depending on the line number) - example a 12 bits per sample JPEG would be rendered without fault into a screen full of random memory garbage.
Assembling/compiling with the 'jpeg' switch off didn't work, fixed, and also now zeros out the SWI decode values in the module header.
Moved include of 'yuvtabs.s' into the colour conversion code.
Deleted panic_exit, it did nothing useful but trace a value then exit, so it now just calls exit() like everyone else.
Removed excess call to find_image_dims(), this was needed just to get the workspace requirements when the JPEG had already been sized up by asm_find_image_dims() earlier. Side effect of removing the pilot JPEG code earlier is that this call can now only get to the JPEG code from a JPEG_ SWI. Changed to just pass the workspace requirements into 'c.PutScaled' and save a duplicate scan.
Fatal exits from the assembler huffman decoder now report a sensible error.
Trimmed out all the JPEG assessment code from 'c.PutScaled' and moved it into 'c.rojpeg' so the put scaled is only concerned with putting things scaled.
Sanitised the #includes a bit.
Fixed on last check of wp->save_mode looking at the wrong bits for the mode number.
Resolved all the warning in the genhdr/genyuvtabs/genpalette utilities by casting a bit harder.[A[B
Added new more descriptive error messages to the messages file (not currently used), and made the 'not supported by' ones consistent so the tokeniser might crunch the file a bit more.
In looks_like_jpeg() changed a bitwise to logical or.
Fixed longstanding problem of not being able to render JPEGs at a scale of less than 1/6 in any greyscale mode, because, err, there was no code to do it - only the colour case was checked for. Implemented for 8bpp grey and 32bpp grey (which gets dithered for other lower modes) by just converting the luma channel into an equally weighted RGB value or replicating it for 256 greys.
Tested in all 8 colour depths on a Risc PC using sampling ratios of 1x1; 2x1; 1x2; 2x2 of the IJG test image scaled in !Draw by 0.16.

Version 1.32. Tagged as 'SprExtend-1_32'

Function asm_get_image_dims returns width in r2, was using r0, so version 1.30 would leave shadows in !Draw. Changed to use r2.

Version 1.31. Tagged as 'SprExtend-1_31'

During the original development (referred to in the docs as Sprite Extend 2) JPEG data was briefly wrapped inside a sprite file before the JPEG_ swis were introduced. Within SpriteExtend some code still remained to fake a mode 20 sprite header with the JPEG output sized adjusted as though it was 4bpp, then later undo the faking by checking for a mode 20 sprite with is_it_jpeg set.
This version removes all of the code looking out for pilot JPEGs, and rationalises the fake sprite header to just report the true X/Y size.
Fix bug where r4 would be corrupted on exit from JPEG_PlotScaled if an error occurred, and generally rationalised the exit cases a bit more sensibly.
Made the JPEG_ swi despatch a bit more simple to follow.
Corrected a comment in the NSM_bpptable.
Deleted unused 'ecfspace' from the workspace.
Hid the 'macroword' from the C code as it's now an assembler only value.
Cut the initial comments from c/putscaled and placed in Docs.
Cut the debug tracing code (a notable %age) from c/putscaled and placed in tracing support file.
Simplified the entry to putscaled_compiler() now we don't have to look out for pilot format JPEGs within sprites any more.
Sprinkled in some block comments to make navigating the c/putscaled file a bit easier.

Version 1.30. Tagged as 'SprExtend-1_30'

No code change - not tagged.

2000 lines of unloved code from 1993 deleted, binary still the same afterwards, so should be same as 1.25.

Version 1.26. Tagged as 'SprExtend-1_26'

1 pixel wide JPEGs:
The diffuse dithering code considers all lines as 1-N-1 where N can be zero and the first and last pixel are dealt with specially because there's no data to scatter beyond the edge.
With a 1 pixel wide JPEG the dithering code ended up with a -ve number in the X counter and wandered off the end of memory. Fix just moves a SUB up a few lines and turns it into a SUBS so that the 1 wide case becomes 0-N-1 with N=0.
1 pixel high sprites:
With output switched to a 1 pixel high sprite an abort would quickly follow because the read of mode variables had a backdoor check to workaround a bug in RISC OS 2.00 which returned a duff value for YWindLimit in MODE 22. As the definition of MODE 22 got changed to 768x288 in RISC OS 3.xx (and the YWindLimit bug fixed) this code now just falsely reported a 1 pixel high sprite as being 1024 high and the blitter splattered all over memory it shouldn't.
Result:
Loss of RISC OS 2.00 compatibility, but can now load JPEGs of Xx1 or 1xY and even 1x1.

Version 1.25. Tagged as 'SprExtend-1_25'

Trim 200+ lines of changes dating back to 1987, combine with non duplicates in the 'BlackLog'.
Use 'offsetof' macro in genjhdr to avoid warnings about uninitialised variables, rename from makejhdr so all the utils are clearly demarked.
Add throwback to MkCFSI-j.
Replace reason codes passed to SWIs with textual equivalents from the respective header files.
Speed up SWI despatch a bit by making the first few debug instructions depend on 'debuggs'.
Qualify all of the debug switches with the global 'debug' one.
Eliminate single use of 'pullx' macro.
Make do_branch() take an unsigned opcode so 50% of the branches don't result in implied cast warnings.
Added an UNUSED() macro to reduce a few of the legitimate warnings (the remainder are either in the original JPEG code or ones that it is worth checking the logic of.
Unixify one last filename.

Version 1.24. Tagged as 'SprExtend-1_24'

Removed braces selecting code from 0.47 0.50 and 0.55, this is over 80
versions ago and just confusing.
Binary the same, not tagged.

Removed local definition of XOS_CLI and XColourTrans_SelectTable, replaced
with header file.

Delete swiv2_old (moved to _old directory)

Changed to use {TRUE} and {FALSE} built in objasm variables.

Label dividebyzero fall through had code in the way for debug = {TRUE}.

Trimmed some dead code and definitions.

Stopped thrashing OS_CLI every time a JPEG plot is required to check
ColourTrans version, this is now done once at startup and a flag kept
instead.

Author: Rob Sprowson

Version 1.19. Tagged as 'SprExtend-1_19'