From 5e72526da4e915791f03af056890e16821bde052 Mon Sep 17 00:00:00 2001 From: silverwind Date: Mon, 19 Feb 2024 03:23:06 +0100 Subject: [PATCH] Downscale pasted PNG images based on metadata (#29123) Some images like MacOS screenshots contain [pHYs](http://www.libpng.org/pub/png/book/chapter11.html#png.ch11.div.8) data which we can use to downscale uploaded images so they render in the same dppx ratio in which they were taken. Before: image After: image --- web_src/js/features/comp/ImagePaste.js | 20 +++++++++-- web_src/js/utils/image.js | 47 ++++++++++++++++++++++++++ web_src/js/utils/image.test.js | 29 ++++++++++++++++ 3 files changed, 93 insertions(+), 3 deletions(-) create mode 100644 web_src/js/utils/image.js create mode 100644 web_src/js/utils/image.test.js diff --git a/web_src/js/features/comp/ImagePaste.js b/web_src/js/features/comp/ImagePaste.js index 27abcfe56..444ab8915 100644 --- a/web_src/js/features/comp/ImagePaste.js +++ b/web_src/js/features/comp/ImagePaste.js @@ -1,5 +1,7 @@ import $ from 'jquery'; +import {htmlEscape} from 'escape-goat'; import {POST} from '../../modules/fetch.js'; +import {imageInfo} from '../../utils/image.js'; async function uploadFile(file, uploadUrl) { const formData = new FormData(); @@ -109,10 +111,22 @@ const uploadClipboardImage = async (editor, dropzone, e) => { const placeholder = `![${name}](uploading ...)`; editor.insertPlaceholder(placeholder); - const data = await uploadFile(img, uploadUrl); - editor.replacePlaceholder(placeholder, `![${name}](/attachments/${data.uuid})`); - const $input = $(``).attr('id', data.uuid).val(data.uuid); + const {uuid} = await uploadFile(img, uploadUrl); + const {width, dppx} = await imageInfo(img); + + const url = `/attachments/${uuid}`; + let text; + if (width > 0 && dppx > 1) { + // Scale down images from HiDPI monitors. This uses the tag because it's the only + // method to change image size in Markdown that is supported by all implementations. + text = `${htmlEscape(name)}`; + } else { + text = `![${name}](${url})`; + } + editor.replacePlaceholder(placeholder, text); + + const $input = $(``).attr('id', uuid).val(uuid); $files.append($input); } }; diff --git a/web_src/js/utils/image.js b/web_src/js/utils/image.js new file mode 100644 index 000000000..ed5d98e35 --- /dev/null +++ b/web_src/js/utils/image.js @@ -0,0 +1,47 @@ +export async function pngChunks(blob) { + const uint8arr = new Uint8Array(await blob.arrayBuffer()); + const chunks = []; + if (uint8arr.length < 12) return chunks; + const view = new DataView(uint8arr.buffer); + if (view.getBigUint64(0) !== 9894494448401390090n) return chunks; + + const decoder = new TextDecoder(); + let index = 8; + while (index < uint8arr.length) { + const len = view.getUint32(index); + chunks.push({ + name: decoder.decode(uint8arr.slice(index + 4, index + 8)), + data: uint8arr.slice(index + 8, index + 8 + len), + }); + index += len + 12; + } + + return chunks; +} + +// decode a image and try to obtain width and dppx. If will never throw but instead +// return default values. +export async function imageInfo(blob) { + let width = 0; // 0 means no width could be determined + let dppx = 1; // 1 dot per pixel for non-HiDPI screens + + if (blob.type === 'image/png') { // only png is supported currently + try { + for (const {name, data} of await pngChunks(blob)) { + const view = new DataView(data.buffer); + if (name === 'IHDR' && data?.length) { + // extract width from mandatory IHDR chunk + width = view.getUint32(0); + } else if (name === 'pHYs' && data?.length) { + // extract dppx from optional pHYs chunk, assuming pixels are square + const unit = view.getUint8(8); + if (unit === 1) { + dppx = Math.round(view.getUint32(0) / 39.3701) / 72; // meter to inch to dppx + } + } + } + } catch {} + } + + return {width, dppx}; +} diff --git a/web_src/js/utils/image.test.js b/web_src/js/utils/image.test.js new file mode 100644 index 000000000..ba4758250 --- /dev/null +++ b/web_src/js/utils/image.test.js @@ -0,0 +1,29 @@ +import {pngChunks, imageInfo} from './image.js'; + +const pngNoPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAAAAAA6fptVAAAADUlEQVQIHQECAP3/AAAAAgABzePRKwAAAABJRU5ErkJggg=='; +const pngPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAIAAAD91JpzAAAACXBIWXMAABYlAAAWJQFJUiTwAAAAEElEQVQI12OQNZcAIgYIBQAL8gGxdzzM0A=='; +const pngEmpty = 'data:image/png;base64,'; + +async function dataUriToBlob(datauri) { + return await (await globalThis.fetch(datauri)).blob(); +} + +test('pngChunks', async () => { + expect(await pngChunks(await dataUriToBlob(pngNoPhys))).toEqual([ + {name: 'IHDR', data: new Uint8Array([0, 0, 0, 1, 0, 0, 0, 1, 8, 0, 0, 0, 0])}, + {name: 'IDAT', data: new Uint8Array([8, 29, 1, 2, 0, 253, 255, 0, 0, 0, 2, 0, 1])}, + {name: 'IEND', data: new Uint8Array([])}, + ]); + expect(await pngChunks(await dataUriToBlob(pngPhys))).toEqual([ + {name: 'IHDR', data: new Uint8Array([0, 0, 0, 2, 0, 0, 0, 2, 8, 2, 0, 0, 0])}, + {name: 'pHYs', data: new Uint8Array([0, 0, 22, 37, 0, 0, 22, 37, 1])}, + {name: 'IDAT', data: new Uint8Array([8, 215, 99, 144, 53, 151, 0, 34, 6, 8, 5, 0, 11, 242, 1, 177])}, + ]); + expect(await pngChunks(await dataUriToBlob(pngEmpty))).toEqual([]); +}); + +test('imageInfo', async () => { + expect(await imageInfo(await dataUriToBlob(pngNoPhys))).toEqual({width: 1, dppx: 1}); + expect(await imageInfo(await dataUriToBlob(pngPhys))).toEqual({width: 2, dppx: 2}); + expect(await imageInfo(await dataUriToBlob(pngEmpty))).toEqual({width: 0, dppx: 1}); +});