add test for pngInfo

Author: silverwind

web_src/js/utils/image.js

@@ -1,6 +1,6 @@
 export function pngChunks(data) {
   const view = new DataView(data.buffer, 0);
-  if (view.getBigUint64(0) !== 9894494448401390090n) throw new Error(`Invalid png header`);
+  if (view.getBigUint64(0) !== 9894494448401390090n) throw new Error('Invalid png header');
 
   const decoder = new TextDecoder();
   const chunks = [];

web_src/js/utils/image.test.js

@@ -1,4 +1,4 @@
-import {pngChunks} from './image.js';
+import {pngChunks, pngInfo} from './image.js';
 
 test('pngChunks', async () => {
   const blob = await (await globalThis.fetch('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAAAAAA6fptVAAAADUlEQVQIHQECAP3/AAAAAgABzePRKwAAAABJRU5ErkJggg==')).blob();
@@ -8,3 +8,8 @@ test('pngChunks', async () => {
     {name: 'IEND', data: new Uint8Array([])},
   ]);
 });
+
+test('pngInfo', async () => {
+  const blob = await (await globalThis.fetch('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAIAAAD91JpzAAAACXBIWXMAABYlAAAWJQFJUiTwAAAAEElEQVQI12OQNZcAIgYIBQAL8gGxdzzM0A==')).blob();
+  expect(await pngInfo(blob)).toEqual({dppx: 2, width: 2});
+});