I made this short video to demonstrate how to reveal a hidden image using the free image manipulation program GIMP. Unfortunately, the menu items in this screen capture are very small, so identifying them is difficult. Since that’s the case, I will first explain the steps. Then you can watch the video to see how the processes are applied. This  technique is used throughout my Trithemian Web™ Cryptograms to reveal images, linear graphics and text.

All Trithemian Web™ Cryptograms came with extensive documentation detailing how to reveal blended images and solve the cryptogram. A reveal.pdf file includes the RGB numbers needed to reveal a blended image in a selected container. The RGB numbers needed to reveal the image in this sample blue container are 0  51  155.

The sample container is a single, navy blue .png file.

I go to File/Open Recent to open the sample file. The sample is opened at 33% of its actual size. To locate a pixel having the color 0  51  155, I select the Color Picker tool and click anywhere in the blue container. A Color Picker Box with open showing the RGB numbers.

This blue container is made up of two colors. One is 0  51  155. The other is 0  51 153. I left click the Color Picker tool in different locations until I read 0  51  155 in the Color Picker Box.

Now I need to be able to identify that pixel’s precise location. I do that by placing a vertical and horizontal Guide Line.

On the Main Menu I click on Image and then select Guides/New Guide. I set  a vertical guide using the X coordinate values indicated in the Color Picker Box. I then set a horizontal guide using the Y coordinate values indicated in the Color Picker Box.

I have now marked the coordinates of that particular pixel. I increase the container’s viewing size to 200% to more easily see the guide line intersection.

I now click on the Select By Color tool. I move the tool’s cross precisely over the intersection of the guide lines and left click. After a few seconds a mask will appear. I then select the Bucket Fill tool and fill the mask with black.

On the Main Menu I click on Edit and then select Copy. I click on Edit again and select Paste As/New Image.

I now click on Image and select Flatten Image which gives us a white background.

There you have it. The blended image has been revealed. Try a Trithemian Web™ Cryptogram Sample.