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	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: <img width="584" alt="image" src="https://github.com/go-gitea/gitea/assets/115237/50979e3a-5d5a-40dc-a0a4-36eb6e28f14a"> After: <img width="329" alt="image" src="https://github.com/go-gitea/gitea/assets/115237/0690902a-f2fe-4c6b-97b3-6fdd67c21bad">
		
			
				
	
	
		
			30 lines
		
	
	
		
			1.5 KiB
		
	
	
	
		
			JavaScript
		
	
	
	
	
	
			
		
		
	
	
			30 lines
		
	
	
		
			1.5 KiB
		
	
	
	
		
			JavaScript
		
	
	
	
	
	
import {pngChunks, imageInfo} from './image.js';
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const pngNoPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAAAAAA6fptVAAAADUlEQVQIHQECAP3/AAAAAgABzePRKwAAAABJRU5ErkJggg==';
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const pngPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAIAAAD91JpzAAAACXBIWXMAABYlAAAWJQFJUiTwAAAAEElEQVQI12OQNZcAIgYIBQAL8gGxdzzM0A==';
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const pngEmpty = 'data:image/png;base64,';
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async function dataUriToBlob(datauri) {
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  return await (await globalThis.fetch(datauri)).blob();
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}
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test('pngChunks', async () => {
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  expect(await pngChunks(await dataUriToBlob(pngNoPhys))).toEqual([
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    {name: 'IHDR', data: new Uint8Array([0, 0, 0, 1, 0, 0, 0, 1, 8, 0, 0, 0, 0])},
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    {name: 'IDAT', data: new Uint8Array([8, 29, 1, 2, 0, 253, 255, 0, 0, 0, 2, 0, 1])},
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    {name: 'IEND', data: new Uint8Array([])},
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  ]);
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  expect(await pngChunks(await dataUriToBlob(pngPhys))).toEqual([
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    {name: 'IHDR', data: new Uint8Array([0, 0, 0, 2, 0, 0, 0, 2, 8, 2, 0, 0, 0])},
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    {name: 'pHYs', data: new Uint8Array([0, 0, 22, 37, 0, 0, 22, 37, 1])},
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    {name: 'IDAT', data: new Uint8Array([8, 215, 99, 144, 53, 151, 0, 34, 6, 8, 5, 0, 11, 242, 1, 177])},
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  ]);
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  expect(await pngChunks(await dataUriToBlob(pngEmpty))).toEqual([]);
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});
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test('imageInfo', async () => {
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  expect(await imageInfo(await dataUriToBlob(pngNoPhys))).toEqual({width: 1, dppx: 1});
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  expect(await imageInfo(await dataUriToBlob(pngPhys))).toEqual({width: 2, dppx: 2});
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  expect(await imageInfo(await dataUriToBlob(pngEmpty))).toEqual({width: 0, dppx: 1});
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});
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