Refine EXIF text formatting

__tests__/exif.test.ts

@@ -0,0 +1,29 @@
+import { formatExposureCompensation, formatExposureTime } from '@/utility/exif';
+
+describe('EXIF', () => {
+  describe('formats', () => {
+    it('exposure time', () => {
+      expect(formatExposureTime(0)).toBe(undefined);
+      expect(formatExposureTime(undefined)).toBe(undefined);
+      expect(formatExposureTime(0.5)).toBe('1/2s');
+      expect(formatExposureTime(0.1)).toBe('1/10s');
+      expect(formatExposureTime(0.01)).toBe('1/100s');
+      expect(formatExposureTime(1)).toBe('1s');
+      expect(formatExposureTime(1.5)).toBe('1.5s');
+    });
+    it('exposure compensation', () => {
+      expect(formatExposureCompensation(-1)).toBe('-1ev');
+      expect(formatExposureCompensation(0)).toBe(undefined);
+      expect(formatExposureCompensation(0.33)).toBe('+1/3ev');
+      expect(formatExposureCompensation(0.333)).toBe('+1/3ev');
+      expect(formatExposureCompensation(0.5)).toBe('+1/2ev');
+      expect(formatExposureCompensation(0.66)).toBe('+2/3ev');
+      expect(formatExposureCompensation(0.67)).toBe('+2/3ev');
+      expect(formatExposureCompensation(0.015625)).toBe('+1/64ev');
+      expect(formatExposureCompensation(-0.015625)).toBe('-1/64ev');
+      expect(formatExposureCompensation(1)).toBe('+1ev');
+      expect(formatExposureCompensation(1.5)).toBe('+1 1/2ev');
+      expect(formatExposureCompensation(1.9960938)).toBe('+2ev');
+    });
+  });
+});

src/photo/PhotoLarge.tsx

@@ -90,17 +90,20 @@ export default function PhotoLarge({
                   {photo.focalLengthIn35MmFormatFormatted &&
                     <>
                       {' '}
-                      <span className={cc(
-                        'text-gray-400/80',
-                        'dark:text-gray-400/50',
-                      )}>
+                      <span
+                        className={cc(
+                          'text-gray-400/80',
+                          'dark:text-gray-400/50',
+                        )}
+                        title="35mm equivalent"
+                      >
                         {photo.focalLengthIn35MmFormatFormatted}
                       </span>
                     </>}
                 </li>
                 <li>{photo.fNumberFormatted}</li>
-                <li>{photo.isoFormatted}</li>
                 <li>{photo.exposureTimeFormatted}</li>
+                <li>{photo.isoFormatted}</li>
                 <li>{photo.exposureCompensationFormatted ?? '—'}</li>
               </ul>}
             <div className={cc(

src/utility/exif.ts

@@ -1,4 +1,5 @@
 import type { ExifData } from 'ts-exif-parser';
+import { formatNumberToFraction } from './number';
 
 const OFFSET_REGEX = /[+-]\d\d:\d\d/;
 
@@ -18,33 +19,19 @@ export const formatAperture = (aperture?: number) =>
 export const formatIso = (iso?: number) =>
   iso ? `ISO ${iso}` : undefined;
 
-export const formatExposureTime = (exposureTime?: number) =>
-  exposureTime
-    ? `Shutter 1/${Math.floor(1 / (exposureTime ?? 1))}`
+export const formatExposureTime = (exposureTime = 0) =>
+  exposureTime > 0
+    ? exposureTime < 1
+      ? `1/${Math.floor(1 / exposureTime)}s`
+      : `${exposureTime}s`
     : undefined;
 
-const fractionForDecimal = (decimal: number, fractionCharacter?: boolean) => {
-  switch (Math.abs(Math.floor(decimal * 100))) {
-  case 33:
-    return fractionCharacter ? '⅓' : '1/3';
-  case 50:
-    return fractionCharacter ? '½' : '1/2';
-  case 66:
-  case 67:
-    return fractionCharacter ? '⅔' : '2/3';
-  }
-};
-
 export const formatExposureCompensation = (exposureCompensation?: number) => {
   if (
     exposureCompensation &&
-    Math.abs(exposureCompensation) >= 0.33
+    Math.abs(exposureCompensation) > 0.01
   ) {
-    const decimal = exposureCompensation % 1;
-    const whole = Math.abs(exposureCompensation - decimal);
-    const fraction = fractionForDecimal(decimal);
-    const sign = exposureCompensation > 0 ? '+' : '-';
-    return `${sign}${whole ? `${whole} ` : ''}${fraction ?? ''} EV`;
+    return `${formatNumberToFraction(exposureCompensation)}ev`;
   } else {
     return undefined;
   }

src/utility/number.ts

@@ -5,3 +5,46 @@ export const toFixedNumber = (
   const pow = Math.pow(base ?? 10, digits);
   return Math.round(number * pow) / pow;
 };
+
+const gcd = (a: number, b: number): number => {
+  if (b <= 0.0000001) {
+    return a;
+  } else {
+    return gcd(b, a % b);
+  }
+};
+
+const formatDecimalToFraction = (decimal: number) => {
+  if (Math.abs(decimal - 0.33) < 0.011) {
+    return '1/3';
+  } else if (Math.abs(decimal - 0.66) <= 0.011) {
+    return '2/3';
+  } else {
+    const length = decimal.toString().length - 2;
+
+    let denominator = Math.pow(10, length);
+    let numerator = decimal * denominator;
+    
+    const divisor = gcd(numerator, denominator);
+  
+    numerator /= divisor;
+    denominator /= divisor;
+  
+    return `${Math.floor(numerator)}/${Math.floor(denominator)}`;
+  }
+};
+
+export const formatNumberToFraction = (number: number) => {
+  const decimal = (1 - number % 1) > 0.01
+    ? number % 1
+    : 0;
+  const integer = Math.round(Math.abs(number - decimal));
+  const fraction = decimal !== 0
+    ? formatDecimalToFraction(Math.abs(decimal))
+    : '';
+  const sign = number > 0 ? '+' : '-';
+  const whole = integer > 0
+    ? fraction ? `${integer} ` : integer
+    : '';
+  return `${sign}${whole}${fraction}`;
+};