feat(genai): Adding imggen samples

[Guiners]

Description

Fixes #

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Checklist

• I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• Tests pass: npm test (see Testing)
• Lint pass: npm run lint (see Style)
• Required CI tests pass (see CI testing)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This pull request is from a branch created directly off of GoogleCloudPlatform/nodejs-docs-samples. Not a fork.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new sample directory, and I created GitHub Actions workflow for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

Note: Any check with (dev), (experimental), or (legacy) can be ignored and should not block your PR from merging (see CI testing).

[snippet-bot]

Here is the summary of changes.

You are about to add 6 region tags.

• genai/image-generation/imggen-canny-ctrl-type-with-txt-img.js:17, tag googlegenaisdk_imggen_canny_ctrl_type_with_txt_img
• genai/image-generation/imggen-raw-reference-with-txt-img.js:15, tag googlegenaisdk_imggen_raw_reference_with_txt_img
• genai/image-generation/imggen-scribble-ctrl-type-with-txt-img.js:17, tag googlegenaisdk_imggen_scribble_ctrl_type_with_txt_img
• genai/image-generation/imggen-style-reference-with-txt-img.js:17, tag googlegenaisdk_imggen_style_reference_with_txt_img
• genai/image-generation/imggen-subj-refer-ctrl-refer-with-txt-imgs.js:17, tag googlegenaisdk_imggen_subj_refer_ctrl_refer_with_txt_imgs
• genai/image-generation/imggen-with-txt.js:17, tag googlegenaisdk_imggen_with_txt

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[gemini-code-assist]

Summary of Changes

Hello @Guiners, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly expands the image generation capabilities demonstrated in the Google GenAI SDK samples. It introduces a suite of new examples that illustrate how to leverage various reference image types—such as Canny, Scribble, Raw, Style, and Subject/Control combinations—to guide and refine the image generation process from text prompts. These additions provide developers with practical, ready-to-use code for advanced image manipulation and creation, complete with corresponding tests to validate their functionality.

Highlights

• New Image Generation Samples: Introduced six new samples demonstrating various image generation capabilities using the Google GenAI SDK, including text-to-image generation with different reference image types.
• Reference Image Control Types: Added samples showcasing advanced control over image generation through Canny edge detection, raw reference images, scribble control, style references, and a combination of subject and control references.
• Comprehensive Testing: Each new image generation sample is accompanied by a dedicated test file, ensuring functionality and providing examples for testing image generation outputs.
• GCS Output Utility: A new utility file (imggen-util.js) was added to assist with creating and cleaning up Google Cloud Storage (GCS) URIs for test outputs, streamlining the testing process for image generation.

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[gemini-code-assist]

Code Review

This pull request adds several new samples for image generation with the GenAI SDK, along with corresponding tests. The changes are well-structured and cover various features like control references, style references, and subject references.

I've found a few issues that need addressing:

• There are a couple of critical bugs in genai/image-generation/imggen-raw-reference-with-txt-img.js and genai/test/imggen-util.js that will cause the sample and tests to fail.
• The imggen-raw-reference-with-txt-img.js sample is inconsistent with others in terms of return value and logging.
• There's a minor readability improvement possible in imggen-subj-refer-ctrl-refer-with-txt-imgs.js.

Please see my detailed comments for suggestions on how to fix these.

[iennae]

this assumes that it works and you should check the response rather than just logging.