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Implement mime type sniffing

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This commit is contained in:
Surma
2018-07-16 14:54:48 +01:00
parent b15545402a
commit 0f08121596
6 changed files with 51 additions and 16 deletions
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22
src/codecs/decoders.ts
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@@ -3,12 +3,13 @@ import * as browserPNG from './browser-png/decoder';
import * as browserWebP from './browser-webp/decoder';
import * as wasmWebP from './webp/decoder';
import { sniffMimeType } from '../lib/util';
export interface Decoder {
name: string;
decode(file: File): Promise<ImageBitmap>;
isSupported(): Promise<boolean>;
supportedMimeTypes: string[];
supportedExtensions: string[];
canHandleMimeType(mimeType: string): boolean;
}
// We load all decoders and filter out the unsupported ones.
@@ -19,9 +20,9 @@ export const decodersPromise: Promise<Decoder[]> = Promise.all(
wasmWebP,
browserWebP,
]
.map(async (encoder) => {
if (await encoder.isSupported()) {
return encoder;
.map(async (decoder) => {
if (await decoder.isSupported()) {
return decoder;
}
return null;
}),
@@ -31,12 +32,9 @@ export const decodersPromise: Promise<Decoder[]> = Promise.all(
export async function findDecoder(file: File): Promise<Decoder | undefined> {
const decoders = await decodersPromise;
// Prefer a match on mime type over a match on file extension
const decoder = decoders.find(decoder => decoder.supportedMimeTypes.includes(file.type));
if (decoder) {
return decoder;
const mimeType = await sniffMimeType(file);
if (!mimeType) {
return;
}
return decoders.find(decoder =>
decoder.supportedExtensions.some(extension =>
file.name.endsWith(`.${extension}`)));
return decoders.find(decoder => decoder.canHandleMimeType(mimeType));
}