How Can I Save an Image with CSS Filters Applied on the Canvas Without a Server?

Saving an Image with Applied CSS Filters on Canvas Without a Backend

To save an image with CSS filters applied on the client-side, follow these steps:

Convert to Canvas and Extract Image Data

1. Convert the image to a canvas using document.getElementById("myCanvas").getContext("2d").drawImage(image, 0, 0, canvas.width, canvas.height);.
2. Extract the image data with applied filters using myCanvas.toDataURL("image/png").

Apply CSS Filters to Context

However, the image will be saved without effects if the context filter property is not supported. To address this:

1. Check for the existence of the context.filter property using typeof ctx.filter === "undefined".
2. If supported, apply CSS filters using ctx.filter = "filterValue" before drawing the image to the canvas.
3. If not supported, manually apply filters using an alternative method not shown here.

Example

This example applies a sepia filter to an image using the filter property. If not supported, it would use a fallback (not shown).

var img = new Image();
img.crossOrigin = "";
img.onload = draw;
img.src = "//i.imgur.com/WblO1jx.jpg";

function draw() {
  var canvas = document.querySelector("canvas"),
    ctx = canvas.getContext("2d");

  canvas.width = this.width;
  canvas.height = this.height;

  // filter
  if (typeof ctx.filter === "undefined") {
    ctx.filter = "sepia(0.8)";
    ctx.drawImage(this, 0, 0);
  } else {
    ctx.drawImage(this, 0, 0);
    // TODO: manually apply filter here.
  }

  document.querySelector("img").src = canvas.toDataURL();
}

Remember, CSS filters only apply to the elements' appearance, not the actual bitmap data. To apply actual filters, work with the bitmap at pixel level if the filter property is not available.

The above is the detailed content of How Can I Save an Image with CSS Filters Applied on the Canvas Without a Server?. For more information, please follow other related articles on the PHP Chinese website!