Messages in this thread | | | Date | Thu, 15 Feb 2024 11:46:21 +0100 | Subject | Re: [PATCH v5 07/13] drm/mediatek: Support alpha blending in display driver | From | AngeloGioacchino Del Regno <> |
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Il 15/02/24 11:11, Hsiao Chien Sung ha scritto: > Support "Pre-multiplied" and "None" blend mode on MediaTek's chips by > adding correct blend mode property when the planes init. > Before this patch, only the "Coverage" mode (default) is supported. > > For more information, there are three pixel blend modes in DRM driver: > "None", "Pre-multiplied", and "Coverage". > > To understand the difference between these modes, let's take a look at > the following two approaches to do alpha blending: > > 1. Straight: > dst.RGB = src.RGB * src.A + dst.RGB * (1 - src.A) > This is straightforward and easy to understand, when the source layer is > compositing with the destination layer, it's alpha will affect the > result. This is also known as "post-multiplied", or "Coverage" mode. > > 2. Pre-multiplied: > dst.RGB = src.RGB + dst.RGB * (1 - src.A) > Since the source RGB have already multiplied its alpha, only destination > RGB need to multiply it. This is the "Pre-multiplied" mode in DRM. > > For the "None" blend mode in DRM, it means the pixel alpha is ignored > when compositing the layers, only the constant alpha for the composited > layer will take effects. > > Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com> > Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
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