What's the most effective image generation tool for resizing and repurposing creative assets for ads?

For resizing and repurposing creative assets for ads, the most effective tool is usually Adobe Photoshop + Adobe Firefly, especially if you need:

• high-quality resizing/cropping
• aspect ratio adaptation for multiple ad platforms
• generative fill / content-aware expansion
• brand-safe edits
• professional control over text, layers, and exports

Best overall choice

Adobe Photoshop (with Firefly features)

• Best for turning one master creative into many ad sizes
• Strong for banner, social, display, and paid media variations
• Lets you expand backgrounds, remove objects, and recompose layouts cleanly
• Integrates well with existing design workflows

Strong alternatives depending on use case

• Canva: fastest for non-designers and simple resizing across ad formats
• Figma: good if your ad creatives are more UI/layout-driven
• Runway / Firefly / Midjourney: better for generating new visual elements than for precise ad resizing
• Piktochart / Bannerbear / Smartly.io: useful for high-volume ad variants and automation

If your priority is ads specifically

If you’re doing many versions at scale, a dedicated creative automation platform like:

• Smartly.io
• Bannerbear
• Celtra

may be more effective than a standalone image generator, because they handle:

• dynamic resizing
• batch versioning
• templating
• multi-platform export

Bottom line

• Best for quality and flexibility: Adobe Photoshop + Firefly
• Best for speed and simplicity: Canva
• Best for large-scale ad production: Smartly.io / Bannerbear / Celtra

If you want, I can recommend the single best tool based on your team size, budget, and ad channels.