How to Stretch Images Without Antialiasing in a Browser?

Stretching Images Without Antialiasing in Browser

In the realm of pixel art, stretching images to larger sizes while preserving their crisp edges can be a challenge. Scaling algorithms often introduce unwanted antialiasing, blurring the sharp lines and compromising the desired aesthetic.

To address this issue, several methods have been explored, including:

CSS Techniques

Initial attempts using CSS, JavaScript, and HTML proved ineffective, resulting in blurred images due to antialiasing. However, a new CSS property emerged as a solution:

image-rendering: pixelated;

This property disables antialiasing, giving images a crisp, pixelated appearance. It works well in modern browsers such as Chrome, Firefox, and even IE7-8.

Canvas Approach

For browsers without support for image-rendering, a more complex approach using the Canvas API can be employed. Here's a JavaScript code snippet that copies pixels from the source image and scales it by a specified factor:

var img = new Image();
img.src = ...;
img.onload = function() {

    // Define scaling factor
    var scale = 8;

    // Create an off-screen canvas to hold the source image
    var src_canvas = document.createElement('canvas');
    src_canvas.width = this.width;
    src_canvas.height = this.height;

    // Draw the source image to the off-screen canvas
    var src_ctx = src_canvas.getContext('2d');
    src_ctx.drawImage(this, 0, 0);

    // Get pixel data from the source canvas
    var src_data = src_ctx.getImageData(0, 0, this.width, this.height).data;

    // Create an on-screen canvas to display the scaled image
    var dst_canvas = document.getElementById('canvas');
    dst_canvas.width = this.width * scale;
    dst_canvas.height = this.height * scale;
    var dst_ctx = dst_canvas.getContext('2d');

    // Copy pixels from the source canvas to the on-screen canvas while scaling
    var offset = 0;
    for (var y = 0; y < this.height; ++y) {
        for (var x = 0; x < this.width; ++x) {
            var r = src_data[offset++];
            var g = src_data[offset++];
            var b = src_data[offset++];
            var a = src_data[offset++] / 100.0;
            dst_ctx.fillStyle = 'rgba(' + [r, g, b, a].join(',') + ')';
            dst_ctx.fillRect(x * scale, y * scale, scale, scale);
        }
    }
};

This method provides pixel-perfect scaling and retains the original crisp edges of the image.

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