RenderTargetTexture to Image Blob but image can't readable

Hello guys
I want to capture a screenshot that has different resolution from main view resolution but not affected to main screen’s view like resizing. ex) 1367 x 621 canvas but screenshot is 1920 x 1080 but there’s no resizing

  1. Make a WebGLRenderTarget to render different pixel from main screen
  2. render to RenderTarget
  3. Read Pixel of it
  4. Convert to blob for download screenshot ← Here is a problem
    ImageBlob can’t open with Warning
    here’s my CodeSandBox

ps. I check that renderTarget was rendered successfully. (make a plane and add to scene, set a map from renderTarget it looks fine)