mirror of https://github.com/vector-im/riot-web
54 lines
2.0 KiB
JavaScript
54 lines
2.0 KiB
JavaScript
/*
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Copyright 2015, 2016 OpenMarket Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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'use strict';
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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 calcuations
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* (e.g. scroll locking)
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*/
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export function thumbHeight(fullWidth, fullHeight, thumbWidth, thumbHeight) {
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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 undefined;
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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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