Answers for "change opacity of image"

css how to make background transparent

/* Use RGBA */
background-color: rgba(255, 255, 0, 0.75); /* Transparent Yellow */

image opacity in html

img {
  opacity: 0.5;
}

change opacity of png

convert  test.png -threshold 0% -alpha off  black_threshold.png

change opacity of png

convert  test.png -threshold 80% -alpha off  black_threshold.png