Moderator: Cartographers
RedBaron0 wrote:And loads of images with watermarks through them...
ender516 wrote:It is not likely to occur in the kind of images/textures/grunge that CC mapmaker use, but it is possible to embed a watermark in a digital image that is essentially invisible but can be recovered in order to establish the provenance of that image. So just because you can't see a watermark, doesn't mean there isn't one.
natty_dread wrote:ender516 wrote:It is not likely to occur in the kind of images/textures/grunge that CC mapmaker use, but it is possible to embed a watermark in a digital image that is essentially invisible but can be recovered in order to establish the provenance of that image. So just because you can't see a watermark, doesn't mean there isn't one.
You mean by steganography?
Those kind of watermarks are essentially destroyed when a texture is applied in the image with the multiply blend mode. The watermark may be found in the layered image, but not in the final .png or .jpg image.
If you want a longer explanation:
Steganography uses the least important bits of the image data (usually, the 2-3 lowest bits in each RGB value) to store hidden images inside other images. When you apply the grunge layer, you are usually using multiply blend mode, which multiplies the RGB values by the RGB values of the layers underneath the grunge layer. Opacity is also reduced, and this screws up with the RGB values in such a way that the data hidden in the least important bits is destroyed. Thus any watermarks hidden in grunge layers won't be visible in the final image.
As for images other than grunge textures, there are softwares & plugins for finding and removing steganography images. However, the same principle applies to these images: if the images are applied with low opacity or different blend modes, the steganography images will be destroyed.
natty_dread wrote:Hehe... this gives me an idea... I could hide all kinds of neat stuff in my maps...
captainwalrus wrote:natty_dread wrote:Hehe... this gives me an idea... I could hide all kinds of neat stuff in my maps...
And spend tons of time putting things in that no one ever sees?
natty_dread wrote:captainwalrus wrote:natty_dread wrote:Hehe... this gives me an idea... I could hide all kinds of neat stuff in my maps...
And spend tons of time putting things in that no one ever sees?
Hardly tons of time, just 2 clicks with the mouse...
natty_dread wrote:Well, I have a plugin for paint.net for detecting and adding steganography to images. It only supports 1-bit b/w or 3-bit colour steganographies, but that's fine, at least it doesn't screw with the image too much.
ender516 wrote:natty_dread wrote:Well, I have a plugin for paint.net for detecting and adding steganography to images. It only supports 1-bit b/w or 3-bit colour steganographies, but that's fine, at least it doesn't screw with the image too much.
I guess the steganographs wouldn't appear when you use BOB to reduce the map opacity, eh? Too bad, really.
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