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SVG to JPG/PNG. The latest in my ongoing series of interactive HTML and JavaScript tools written almost entirely by LLMs. This one lets you paste in (or open-from-file, or drag-onto-page) some SVG and then use that to render a JPEG or PNG image of your desired width.

Screenshot of the SVG to JPEG/PNG tool. It starts with a Browse... option for selecting a file, next to a Load example image link, above a textarea full of SVG code. Then a radio box to select between JPEG and PNG, plus a background color color picker widget next to a checkbox labelled transparent. Then Output width, a number field set to 300. Then a convert SVG button. Below is the classic SVG tiger image, with a Download image link that says 47.38BK. Under that is a Base 64 image tag header with a copy image tag button and some visible HTML for a data:image/jpeg image element.

I built this using Claude 3.5 Sonnet, initially as an Artifact and later in a code editor since some of the features (loading an example image and downloading the result) cannot run in the sandboxed iframe Artifact environment.

Here's the full transcript of the Claude conversation I used to build the tool, plus a few commits I later made by hand to further customize it.

The code itself is mostly quite simple. The most interesting part is how it renders the SVG to an image, which (simplified) looks like this:

// First extract the viewbox to get width/height
const svgElement = new DOMParser().parseFromString(
    svgInput, 'image/svg+xml'
).documentElement;
let viewBox = svgElement.getAttribute('viewBox');
[, , width, height] = viewBox.split(' ').map(Number);

// Figure out the width/height of the output image
const newWidth = parseInt(widthInput.value) || 800;
const aspectRatio = width / height;
const newHeight = Math.round(newWidth / aspectRatio);

// Create off-screen canvas
const canvas = document.createElement('canvas');
canvas.width = newWidth;
canvas.height = newHeight;

// Draw SVG on canvas
const svgBlob = new Blob([svgInput], {type: 'image/svg+xml;charset=utf-8'});
const svgUrl = URL.createObjectURL(svgBlob);
const img = new Image();
const ctx = canvas.getContext('2d');
img.onload = function() {
    ctx.drawImage(img, 0, 0, newWidth, newHeight);
    URL.revokeObjectURL(svgUrl);
    // Convert that to a JPEG
    const imageDataUrl = canvas.toDataURL("image/jpeg");
    const convertedImg = document.createElement('img');
    convertedImg.src = imageDataUrl;
    imageContainer.appendChild(convertedImg);
};
img.src = svgUrl;

Here's the MDN explanation of that revokeObjectURL() method, which I hadn't seen before.

Call this method when you've finished using an object URL to let the browser know not to keep the reference to the file any longer.

Posted 6th October 2024 at 7:57 pm

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