Images can have attacks like diluting, noising, contrast changes and so on. So usually important images will be encrypted using a good algorithm(ex. ECC-Eliptic Curve Crypt). In this current trend, the stegno image is encrypted; for better data security. There are different kind of images like BINARY, Grayscale, RGB, CMYK. There are different kind of stegnography process on these images as well as compression techniques.

Some terms need to know (for image encryption): Dithering, Visual Cryptography(images thro Shares), Compression. hope it will be helpful!! All the best for your research~~

Steganography can be considered a way of encryption. Once a picture is transformed into mathematical representation it can be shuffled anyway you like until you have the information of how and where you applied your techniques. It can be combined with another image, text, sound, or any other signal. When you digitize an image, there are process such as sampling, quantization and encoding. You can play around a lot with digits and mix with other digits during these processes. And there is compression and transformations. Many techniques can be applied to hide the information during this stages. There are good  literatures and articles  in DSP. The ultimate objective of Steganography is to hide the data without knowledge.

the main difference relies on the fact that in cryptography we knew that some thing is encrypted where in stenography the data is hidden which means we may not even aware of existence of hidden message.  A noise in the sound may represent some hidden data or could be just s simple noise. 

Ultimately it  depends on the scenario you wish to apply either. With cryptography there are obvious visual clues, obfuscated data or merely a password entry screen. However, with Steganography the user can send the image to multiple recipients without them even realising that the image contains hidden data, and only the intended recipient can be made aware of this contents and the means of how to extract said data.

Another use of steganography are digital watermarks. Hence, the information attached to a medium provides information about the medium. In some cases this information shall be readable by everyone, like meta-data about where and when a photo was taken. In this case the steganography is reduced to the aspect that the embedded information shall not influence the quality of the medium and therefore be be invisible. In other cases the information shall only be readable by some persons, for example the information who originally bought an MP3. In this case, the quality of the medium shall be untouched while the information can only be read, changed, deleted by some persons. In this sense a watermark is kind of steganography+ because in most case when talking about steganography you don't care if somebody can destroy the information without reading it (for example by recoding a picture).

One general drawback of steganography is the little amount of data you can embed into a medium.

There are three types of data hiding techniques which are cryptography, steganography and watermarking. The application of all the three methods are different.

Cryptography: It means that original data is replaced with some other data using a key which can be recovered only with that key. Applications of cryptography can be ATM cards, computer password, electronic commerce. The algorithm for cryptography must be robust.

Steganography: It is a combination of other language (Stego-Graphy) which means covered writing. Data should be hidden in cover object in such a manner that just by viewing (image or video) or listening (audio), you cannot even judge that there is any data or not. It is used for security communication. Once it is detected that there is any data hidden, complete file can be destroyed so that the data cannot be delivered to the receiver. So the purpose does not accomplished.

Watermarking: It is same like steganography but it can be declared by sender that there is some data hidden (for invisible watermarking) which is a copyright of sender. The algorithm can be robust or fragile depending upon the application.

For more information, you can download my paper as:

https://www.researchgate.net/publication/263709085_Protecting_Copyright_Multimedia_Files_by_Means_of_Digital_Watermarking_A_Review?ev=prf_pub

Conference Paper Protecting Copyright Multimedia Files by Means of Digital Wa...

Steganography and Cryptography are data hiding techniques with different but related fields of applications. Cryptography renders a message illegible by applying encryption protocols whereas steganography hides data within innocuous objects concealing the very existence of anything secret. Since steganography is intented for covert communication, it is useful in situations where the use of encryption and secret communication is banned or restricted. Similarly, there may be situations where information pertaining to a resource is to be kept hidden irrespective of any influence whatsoever (e.g. patient details for a particular medical record). Cryptography fails here as authoritative intervention can forcefully undo the effects of encryption. But steganography protocols can still keep the secret strong. So, it is evident that both cryptography and steganography are applicable towards different situations and requirement. For further clarification please feel free to mail me at [email protected]

Cryptography: The data will be changed to other representation that is not readable or not undrestandable by the readers (man in the middle) , in other word attacer know that there is somthing transmit but can not decrypt unles they know the key and the technique that used for encryption.

Steganography: In steganograpgy transmitted data will not seen, because embedded in a cover. if man in the middle suspect that there some thing in side the cover , the idea of steganography gone.

As a result of the previous talk, Robustness in the cryptography is the main requirement for designing good crypto system, while in steganography the Invisibility is the main requirement.

There is no advantage. This comparison is inherently incorrect because cryptography and steganography are indeed two different tools used for different purposes. 

Security has different aspects, such as confidentiality, integrity and availability, which can be addressed by a number of technical solutions, such as encryption and steganography. For instance, one can use either encryption or steganography to address confidentiality requirements.

In steganography, the interest is in concealing the existence of a message from a third party, while in cryptography the purpose is to make a message unreadable by a third party. In steganographic applications, if the third party detects the presence of the hidden data, they may prevent the transmission of steganographic content, while in cryptographic applications this is not an issue.

The stenography hides the reality of existing exchange information between the receiver and sender. so, not reveal the about the identity of sender and receiver.  While, in cryptography, the sender and transmitter are known

Cryptography convert MSG into non understandable form while steganography hide the existence of message, which is more powerful.

There is no message so no tension....

Cryptography relies on encryption techniques and converts intellible data to unintelligible format whereas steganography  secretly hides data inside some other data/media. 

In case of stego, imperperceptibity is one of the key attributes and because the secret is invisible stays out of suspicion and attracts less attack in comparison to crypto.

I recollect the way ma'am used to characterize crypto, stego, wm in three wards PAIN, RISC, SIR while teching. Though this is not an appropriate answer to the question above, i thought of sharing. .

The goal of cryptography is to ensure 'PAIN'

P- privacy

A-authenticity

I- integrity

N- non repudiation

stego is characterised by 'RISC'

R-robustness

I-imperceptibility

S-security

C-capacity

Whereas invisible watermarking by 'SIR'

S-security

I-imperceptibility

R-robustness

https://www.researchgate.net/publication/301880028_Steganography_--_A_Game_of_Hide_and_Seek_in_Information_Communication?ev=prf_pub

Article Steganography -- A Game of Hide and Seek in Information Communication