[PATCH v2 5/6] gdi32: Partially implement HALFTONE stretch mode.

[Alexandre Julliard]

Zhiyi Zhang <zzhang at codeweavers.com> writes:

> COLORONCOLOR(STRETCH_DELETESCANS) was used in place of HALFTONE. COLORONCOLOR mode may delete rows
> of pixels without trying to preserve information so it will cause Wine to render poorly when the
> destination rectangle is small.
>
> According to tests, HALFTONE mode uses box filter when doing integer downscaling and nearest
> neighbor interpolation when doing upscaling in both horizontally and vertically. In other cases,
> HALFTONE mode uses a lanczos3 like algorithm to interpolate pixels. There are also other heuristics
> involved. For example, shrinking a 2x2 image to 1x1 may not use box filter depending on image data.
> Since this algorithm is undocumented, it's difficult to reverse engineer the original algorithm and
> produce identical results. Instead, this patch uses a naive implementation of bilinear interpolation
> to implement HALFTONE mode and it produces good quality images.
>
> For 8-bit and lower color depth images, nulldrv_StretchBlt should resize the images first and then
> converts color depth.
>
> Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=46375
> Signed-off-by: Zhiyi Zhang <zzhang at codeweavers.com>
> ---
>  dlls/gdi32/dibdrv/bitblt.c     |   7 +
>  dlls/gdi32/dibdrv/dibdrv.h     |   2 +
>  dlls/gdi32/dibdrv/primitives.c | 629 ++++++++++++++++++++++++++++++++-
>  3 files changed, 629 insertions(+), 9 deletions(-)

This is breaking some tests:

tools/runtest -q -P wine -T . -M user32.dll -p dlls/user32/tests/user32_test.exe cursoricon && touch dlls/user32/tests/cursoricon.ok
cursoricon.c:3061: Test failed: Colors do not match, got 0xffff00, expected 0x00ff00, test_index 0, row 0, column 1.
cursoricon.c:3061: Test failed: Colors do not match, got 0xffff00, expected 0x00ff00, test_index 0, row 1, column 0.
cursoricon.c:3071: Test failed: Colors do not match, got 0xffff00, expected 0x00ff00, test_index 0, row 0, column 1.
cursoricon.c:3071: Test failed: Colors do not match, got 0xffff00, expected 0x00ff00, test_index 0, row 1, column 0.
cursoricon.c:3061: Test failed: Colors do not match, got 0x000000, expected 0xffffff, test_index 2, row 0, column 0.
cursoricon.c:3061: Test failed: Colors do not match, got 0x000000, expected 0xffffff, test_index 2, row 0, column 1.
cursoricon.c:3061: Test failed: Colors do not match, got 0x000000, expected 0x555555, test_index 2, row 1, column 0.
cursoricon.c:3071: Test failed: Colors do not match, got 0x000000, expected 0xffffff, test_index 2, row 0, column 0.
cursoricon.c:3071: Test failed: Colors do not match, got 0x000000, expected 0xffffff, test_index 2, row 0, column 1.
cursoricon.c:3071: Test failed: Colors do not match, got 0x000000, expected 0x555555, test_index 2, row 1, column 0.
cursoricon.c:3061: Test failed: Colors do not match, got 0x006000, expected 0x004000, test_index 3, row 0, column 0.
cursoricon.c:3061: Test failed: Colors do not match, got 0x0060f8, expected 0x002000, test_index 3, row 0, column 1.
cursoricon.c:3061: Test failed: Colors do not match, got 0x0080f8, expected 0x004000, test_index 3, row 1, column 0.
cursoricon.c:3061: Test failed: Colors do not match, got 0x008000, expected 0x002000, test_index 3, row 1, column 1.
cursoricon.c:3071: Test failed: Colors do not match, got 0x006000, expected 0x004000, test_index 3, row 0, column 0.
cursoricon.c:3071: Test failed: Colors do not match, got 0x0060f8, expected 0x002000, test_index 3, row 0, column 1.
cursoricon.c:3071: Test failed: Colors do not match, got 0x0080f8, expected 0x004000, test_index 3, row 1, column 0.
cursoricon.c:3071: Test failed: Colors do not match, got 0x008000, expected 0x002000, test_index 3, row 1, column 1.
make: *** [Makefile:125296: dlls/user32/tests/cursoricon.ok] Error 18

-- 
Alexandre Julliard
julliard at winehq.org