Introduction to AI Image Generators

The field of Generative AI for visuals has exploded, fundamentally changing how marketers create assets. We have moved from relying solely on stock photography and expensive photoshoots to generating bespoke imagery on demand. This lesson covers the foundational technologies, the primary tools available today, and the techniques required to control them.

The Science: Diffusion Models

At the core of Midjourney, DALL-E 3, and Stable Diffusion lies the concept of "Diffusion". Unlike earlier GANs (Generative Adversarial Networks) which pitted two neural networks against each other, diffusion models work on the principle of denoising.

During training, the model is shown millions of images (e.g., a photo of a dog) and slowly adds Gaussian noise to them until they are just static. The model learns the mathematical reverse of this process: how to take static and predict where the "dog pixels" should go. When you prompt "A dog in space," the AI starts with random noise and iteratively hallucinates patterns that match your text description (encoded via CLIP) until a clean image emerges.

Tool Landscape: Choosing Your Weapon

• Midjourney: Currently the gold standard for artistic quality, lighting, and photorealism. It runs inside Discord, which can be a UI barrier for some, but its V6 model offers unrivaled aesthetic cohesion. It is "opinionated," meaning it adds its own artistic flair to prompts.
• DALL-E 3: Integrated into ChatGPT Plus and Microsoft Bing. Its strength is semantic understanding. If you ask for "A blue cube on top of a red sphere," DALL-E 3 will get the spatial relationship right almost every time, whereas Midjourney might blend them. It is excellent for rendering legible text within images.
• Stable Diffusion: The open-source champion. It can be run locally on powerful GPUs. Its superpower is "ControlNet," which allows you to guide the generation using poses or sketches, and "LoRAs," which are mini-models trained on specific characters or products.

Prompt Engineering for Images

Text-to-Image prompting requires a different mindset than Text-to-Text.

Parameters are specific commands. Common ones in Midjourney include:
--ar 16:9 (Aspect Ratio)
--v 6.0 (Version selection)
--stylize 1000 (How creative the AI should be)
--no (Negative prompting, e.g., --no blurred)

Advanced Techniques: In-painting & Out-painting

Generation is rarely perfect on the first try. In-painting allows you to select a flawed area (like a hand with six fingers) and tell the AI to regenerate just that distinct patch. Out-painting (Zoom Out) allows you to extend the canvas, useful for resizing square social posts into landscape website banners without cropping.