From: Thomas Zimmermann Date: Tue, 3 Jun 2025 16:11:50 +0000 (+0200) Subject: drm/format-helper: Normalize BT.601 factors to 256 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a979a54165c224f3a469b59dcbd2e9754e7e0f41;p=thirdparty%2Flinux.git drm/format-helper: Normalize BT.601 factors to 256 BT.601 weights RGB components by certain factors to convert the color to grayscale. Normalize the constants to 256 instead of 10. Allows for slightly more precise rounding. The division by 256 can be compiled as an 8-bit shift, which might be faster on some hardware. Signed-off-by: Thomas Zimmermann Acked-by: Javier Martinez Canillas Link: https://lore.kernel.org/r/20250603161158.423962-1-tzimmermann@suse.de --- diff --git a/drivers/gpu/drm/drm_format_internal.h b/drivers/gpu/drm/drm_format_internal.h index 9f857bfa368d1..3020ff267513f 100644 --- a/drivers/gpu/drm/drm_format_internal.h +++ b/drivers/gpu/drm/drm_format_internal.h @@ -42,7 +42,7 @@ static inline u32 drm_pixel_xrgb8888_to_r8_bt601(u32 pix) u32 b = pix & 0x000000ff; /* ITU-R BT.601: Y = 0.299 R + 0.587 G + 0.114 B */ - return (3 * r + 6 * g + b) / 10; + return (77 * r + 150 * g + 29 * b) / 256; } static inline u32 drm_pixel_xrgb8888_to_rgb332(u32 pix)