A recursive algorithm to hide three secret images in one image using wavelet transforms

الملخص EN

High power pulsed Neodymium doped Yttrium Aluminum Garnet-(Nd–YAG)-laser with 1J power was used to fuse coatings containing a mixture of FeAlO and Al.

This mixture produced by aluminizing pack cementation treatment and thermal spray of low alloy steel, That is for Studying the mechanical, surface and metallurgical properties for each coating system, and to make a comparison before and after irradiation, and also the specified properties including the coating thickness.

Aluminum Coated samples were made by two advanced techniques pack cementation and thermal spray methods in order to compare the resulted coating layer properties before and after irradiation, and also to determine the technique role from one hand, also fusing effect and thermal residual stresses This paper presents an algorithm based on wavelet transform to hide three secret colored or gray-scale images with different sizes in one colored cover image.

The algorithm takes level1 wavelet transformation for the cover image and level2 wavelet transformation for the coefficients resultant from level1.

The algorithm begins to divide and transpose the secret images into multiple sub bands, then imbedding them into the coefficient parts resulting from level2.

The embedding depends upon a variable threshold which begins with a very small value.

Here the algorithm ensures the embedding of all the pixels values of the sub band, if it is not, the operation will be repeated with a larger threshold value until all the pixels are embedded.

Also the pixel's value will not be embedded directly ; the difference between the cover and the secret pixel value will be embedded instead of it after some manipulation (mathematical operations).

All of these factors (divide and transpose the secret images, the variable threshold for each sub band and changes on the embedded pixels) increase the robustness and quality of the algorithm.

The resultant stage image and the extracted secret images are very close to the original one with high PSNR, high Correlation, low Normal Absolute Error and low Maximum Difference.