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Bug 4290

Summary: fastpath BlitNtoN
Product: SDL Reporter: Sylvain <sylvain.becker>
Component: *don't know*Assignee: Ryan C. Gordon <icculus>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: sezeroz
Version: don't know   
Hardware: All   
OS: All   
Attachments: test case
patch

Description Sylvain 2018-10-02 10:15:46 UTC 
Created attachment 3334 [details]
test case

I have also this patch to add fast paths to BlitNtoN

- when you expand to a pixel format of size 24 to 32.
- when you remove an alpha channel and switch RGB to BGR.

Seems to be 7 or 8 times faster.
Comment 1 Sylvain 2018-10-02 10:16:48 UTC 
Created attachment 3335 [details]
patch
Comment 2 Ozkan Sezer 2018-10-02 12:14:21 UTC 
For the "Fastpath: expand 24 -> 32" case, I suggest:
-        int alphashift = alpha << 24;
+        unsigned alphashift = alpha << 24;
Comment 3 Sylvain 2018-10-02 17:53:04 UTC 
Yes you're right
Comment 4 Sylvain 2019-01-24 18:09:42 UTC 
Probably some issue with RGB_24 since it depends on BYTES_ORDER,
then, the code should be moved to normal_blit_3 and normal_blit_4 in SDL_blit_N.c
Comment 5 Sam Lantinga 2019-01-25 09:53:58 UTC 
Yup, can you update the patch with those fixes?
Comment 6 Sylvain 2019-01-30 14:35:56 UTC 
Fixed in 
 https://hg.libsdl.org/SDL/rev/57b136cff952
 https://hg.libsdl.org/SDL/rev/338b02acfdfc

With some more than what was doing the original patch!

I've added an ifdef for little endian, as I'm not 100% sure for big endian.

Probably it can be done by inverting the use of the two function same_rgb / inv_rgb ...