Question:

What are the technical reasons behind the incompatibility of this image with Firefox, while it works in other browsers? (Inspired by a post from r/glitch_art)

: [Here’s the original post].

Answer:

Why This Image Won’t Show Up in Firefox

If you are a fan of glitch art, you might have seen [this image] that works in all major browsers, except Firefox. You might wonder why this is the case, and what are the technical reasons behind this incompatibility. In this article, we will try to explain the mystery of this image, and how it exploits a feature of the JPEG format that Firefox does not support.

JPEG is a popular image format that is widely used on the web. JPEG stands for Joint Photographic Experts Group, which is the name of the committee that created the standard in 1992. JPEG is a lossy compression format, which means that it reduces the file size of an image by discarding some of the information that is not perceptible to the human eye. This allows JPEG images to have high quality and low bandwidth, making them suitable for web applications.

How does JPEG work?

JPEG works by dividing an image into small blocks of 8×8 pixels, and applying a mathematical transformation called Discrete Cosine Transform (DCT) to each block. DCT converts the pixel values into frequency coefficients, which represent how much each block contains different spatial frequencies. The higher the frequency, the more details and edges the block has. The lower the frequency, the more smooth and uniform the block is.

JPEG then quantizes the frequency coefficients, which means that it rounds them to the nearest integer value from a predefined table. The quantization table is designed to preserve more of the low-frequency coefficients, which are more important for the image quality, and discard more of the high-frequency coefficients, which are less noticeable to the human eye. This is where the lossy compression occurs, as some of the information is irreversibly lost.

JPEG then encodes the quantized coefficients using a technique called Huffman coding, which assigns shorter binary codes to more frequent values, and longer codes to less frequent values. This reduces the file size even further, as the most common values take up less space.

What is progressive JPEG?

Progressive JPEG is a variation of JPEG that allows the image to be displayed gradually as it is downloaded. Instead of encoding the image block by block, progressive JPEG encodes the image in multiple scans, each containing a subset of the frequency coefficients. The first scan contains only the lowest frequency coefficient, which represents the average color of each block. The subsequent scans add more coefficients, increasing the details and quality of the image. The final scan contains all the coefficients, resulting in the full image.

Progressive JPEG is useful for slow internet connections, as it gives the user a rough idea of the image before it is fully loaded. It also creates a smooth transition effect, as the image becomes sharper and clearer with each scan.

What is the problem with Firefox?

The problem with Firefox is that it does not support a specific type of progressive JPEG, called spectral selection. Spectral selection allows the encoder to choose which frequency bands to include in each scan, instead of following a fixed order. For example, the encoder can decide to skip some of the high-frequency bands, which are less important for the image quality, and save them for the last scan. This can reduce the file size and improve the compression ratio.

However, Firefox does not implement spectral selection, and expects the progressive JPEG scans to follow the default order. If it encounters a scan that does not match the expected order, it will stop decoding the image, and display a blank or corrupted image. This is what happens with the image that works in all browsers, except Firefox. The image uses spectral selection to create a glitchy effect, by skipping some of the frequency bands and encoding them in the wrong order. This confuses Firefox, and prevents it from displaying the image correctly.

How to fix it?

There are two possible ways to fix this problem. One is to change the image format, and use a different compression method that does not rely on spectral selection. For example, PNG is a lossless format that preserves all the information in the image, and works in all browsers. However, PNG images tend to have larger file sizes than JPEG images, which can affect the loading speed and bandwidth.

Another way is to change the browser, and use a different browser that supports spectral selection. For example, Chrome, Safari, and Edge are browsers that can decode and display the image correctly. However, this might not be feasible for some users, who might prefer to stick with Firefox for various reasons, such as security, privacy, or personal preference.

Conclusion

In this article, we have explained the technical reasons behind the incompatibility of this image with Firefox, while it works in other browsers. We have learned that the image uses a feature of the JPEG format called spectral selection, which Firefox does not support. We have also discussed some possible solutions to fix this problem, such as changing the image format or the browser. We hope that this article has helped you understand the mystery of this image, and appreciate the art of glitch.

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