It is a common misconception that hacking and other slightly “illegal” activities can only be done by the greatest professionals. However, these processes are actually fairly simple to replicate given that one has knowledge of how they work and a decent computer program.
Removing iStock Watermarks
Watermarks are used to prevent people from stealing copyrighted images. They should not be removed if the images will be used for commercial purposes. Credit should still be given to the individual or company who took or created the picture.
Now that that’s out of the way, let’s get to the interesting stuff.
Watermarks are automatically applied by multiplying an image by the watermark “function.” Take the following watermark from iStock, for example.
The watermark was applied by taking the original image and multiplying it to the watermark. This can be seen by splicing out the watermark and subsequently turning it into data. To turn the cropped watermark (named img) into data, the command ImageData[img,”Byte”] can be used. Then, the data (named whiteData) can be multiplied by a sine graph.
To reverse the effect of the watermark, the modified image can be divided by the watermark “function.”
In order to create the inverse image that can delete the watermark, whiteData can by divided by 255 (this is now called whiteDataMask). whiteData must be divided by 255 to ensure the final image will have data from 0 to 255. By multiplying 1/whiteDataMask by img, the watermark will be deleted. Images can be multiplied to each other by using ImageMultiply.
It worked! This method can be applied to other images by using Manipulate to change the position of the mask over the image. Take note that black and white masks must be used to delete the shaded part first, then to re-brighten the image with the white mask.