mirror of https://github.com/vector-im/riot-web
55 lines
2.1 KiB
TypeScript
55 lines
2.1 KiB
TypeScript
/*
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Copyright 2024 New Vector Ltd.
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Copyright 2015, 2016 , 2020 Copyright 2020 The Matrix.org Foundation C.I.C.
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SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
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Please see LICENSE files in the repository root for full details.
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*/
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/**
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* Returns the actual height that an image of dimensions (fullWidth, fullHeight)
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* will occupy if resized to fit inside a thumbnail bounding box of size
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* (thumbWidth, thumbHeight).
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*
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* If the aspect ratio of the source image is taller than the aspect ratio of
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* the thumbnail bounding box, then we return the thumbHeight parameter unchanged.
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* Otherwise we return the thumbHeight parameter scaled down appropriately to
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* reflect the actual height the scaled thumbnail occupies.
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*
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* This is very useful for calculating how much height a thumbnail will actually
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* consume in the timeline, when performing scroll offset calculations
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* (e.g. scroll locking)
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*/
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export function thumbHeight(fullWidth: number, fullHeight: number, thumbWidth: number, thumbHeight: number): number;
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export function thumbHeight(
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fullWidth: number | undefined,
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fullHeight: number | undefined,
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thumbWidth: number,
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thumbHeight: number,
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): null;
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export function thumbHeight(
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fullWidth: number | undefined,
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fullHeight: number | undefined,
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thumbWidth: number,
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thumbHeight: number,
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): number | null {
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if (!fullWidth || !fullHeight) {
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// Cannot calculate thumbnail height for image: missing w/h in metadata. We can't even
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// log this because it's spammy
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return null;
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}
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if (fullWidth < thumbWidth && fullHeight < thumbHeight) {
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// no scaling needs to be applied
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return fullHeight;
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}
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const widthMulti = thumbWidth / fullWidth;
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const heightMulti = thumbHeight / fullHeight;
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if (widthMulti < heightMulti) {
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// width is the dominant dimension so scaling will be fixed on that
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return Math.floor(widthMulti * fullHeight);
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} else {
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// height is the dominant dimension so scaling will be fixed on that
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return Math.floor(heightMulti * fullHeight);
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}
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}
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