Fixes Ticket4053
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes Ticket3170
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: James Almer <jamrial@gmail.com>

Found-by: Kierank
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

sws_getCachedContext is not a full replacement for the function.

Based on a long debug session with Kostya.

The rationale is that you have a packed format in form
<greyscale sample> <alpha sample> <greyscale sample> <alpha sample>
and shortening greyscale to 'G' might make one thing about Greenscale instead.
An alias pixel format and color space name are provided for compatibility.

Fixes part of Ticket3785
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This can help "extreme" resizes, e.g with some 4k stuff.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Prevent a division by zero down the codepath.

Sample-Id: 00001721-google
Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This way all context fields get initialized and can be used without needing to reinit the context
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

swscale/utils: scale filter_size in warning so that it can be used as max for the compile time define
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes ticket #3495.

Both of these dithering methods are from http://pippin.gimp.org/a_dither/ for
GIF they can be considered better than bayer (provides more gray-levels), and
spatial stability - often more than twice as good compression and less visual
flicker than error diffusion methods (the methods also avoids error-shadow
artifacts of diffusion dithers).

These methods are similar to blue/green noise type dither masks; but are
simple enough to generate their mask on the fly. They are still research work
in progress; though more expensive to generate masks (which can be used in a
LUT) like 'void and cluster' and similar methods will yield superior results

Improves rgb -> gray16 conversion

Fixes Ticket3422

The pam and png output files look visually similar, in both cases the
dynamics increase to 0x0 -> 0xfffb.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes Ticket3242
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Fixes artifacts where fast bilinear was used for downscaling chroma
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

makes the first call to sws_getContext() 1ms faster
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Allow some dumb factorizations, slightly decrease spaghetti factor.

Remove duplicated getSubSampleFactors() function. Simplify.

Found-by: wm4
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

See Ticket3028
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Lanczos for general case, sinc for upscaling, Gaussian for
downscaling. According to current literature these scalers
should be the best quality-wise algorithms for each case.

Inspired from a patch by wm4 <nfxjfg@googlemail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>