WeChat power grid avatar turned black and white

We performed an analysis of their grayscale conversion algorithm similar to the one we performed when evaluating WeChat’s OCR filtering to determine which grayscale conversion algorithm, if any, the blacklist-based.

A simple way to compare whether two images are the same is by either hashing their encoded file contents or the values of their pixels using a.

There are different ways of describing images in a way that are invariant to certain transformations such as translation (e.g., moving the position.

We discussed in the OCR section about how machine learning methods, including neural networks and deep learning, can be used to identify the text in an image. In this case, the machine learning algorithms classify each character.

Another way to compare similarity between two images is to treat each as a one-dimensional array of Pixel intensities and then compare these arrays using a similarity metric. Here we investigate three intensity-based similarity.

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6 FAQs about [WeChat power grid avatar turned black and white]

How does WeChat filter images?

WeChat uses two different filtering mechanisms to filter images: an Optical Character Recognition (OCR)-based approach that searches images for sensitive text and a visual-based approach that visually compares an uploaded image against a list of blacklisted images.

Does WeChat use image filtering?

To test if WeChat uses an image filtering algorithm, we changed the aspect ratio of the same 15 sensitive images in two sets. In one set, we reduced each image's height to 70%, and in another, we reduced each image's width to 70%.

Will a blacklisted image be filtered on WeChat?

An image will be filtered on WeChat only if it contains all components of any keyword combination that is blacklisted. To help understand the scope and target of OCR-based image filtering on WeChat, in April 2018, we tested images containing keyword combinations from a sample list.

How do I know if an image is automatically filtered on WeChat Moments?

To determine if an image is automatically filtered on WeChat Moments using an international account, post the image and wait 60 seconds. If the image is not visible to a mainland China phone number after this time, it has likely been automatically filtered. We found that images are typically removed within 5 to 30 seconds after filtering.

Does WeChat use a sliding window approach?

WeChat does not appear to use a sliding window approach for image comparison as suggested by this analysis. Instead, images are compared as a whole, and adding complex patterns outside of a blacklisted image can evade filtering.

Is WeChat image filter invariant?

To test if WeChat uses image features with scale and rotation invariance properties for comparing similarity between images, we tested if WeChat's image filter is invariant to scale and rotation using popular descriptors such as SIFT descriptors and Hu and Zernike moments.

WeChat power grid avatar turned black and white