feat: change pgn opacity

src/pages/tools/image/png/change-opacity/service.ts

@@ -0,0 +1,39 @@
+export async function changeOpacity(
+  file: File,
+  opacity: number
+): Promise<File> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onload = (event) => {
+      const img = new Image();
+      img.onload = () => {
+        const canvas = document.createElement('canvas');
+        const ctx = canvas.getContext('2d');
+        if (!ctx) {
+          reject(new Error('Canvas context not supported'));
+          return;
+        }
+
+        canvas.width = img.width;
+        canvas.height = img.height;
+
+        ctx.clearRect(0, 0, canvas.width, canvas.height);
+        ctx.globalAlpha = opacity;
+        ctx.drawImage(img, 0, 0);
+
+        canvas.toBlob((blob) => {
+          if (blob) {
+            const newFile = new File([blob], file.name, { type: 'image/png' });
+            resolve(newFile);
+          } else {
+            reject(new Error('Failed to generate image blob'));
+          }
+        }, 'image/png');
+      };
+      img.onerror = () => reject(new Error('Failed to load image'));
+      img.src = <string>event.target?.result;
+    };
+    reader.onerror = () => reject(new Error('Failed to read file'));
+    reader.readAsDataURL(file);
+  });
+}