🔗 Issue Links

CIS-2152

🎯 Goal

Use Stream's CDN v2 to improve the memory footprint of the application. Now, images are downloaded with a lower resolution instead of the original one.

📝 Summary

• Stream CDN v2 Implementation
• Add the possibility to limit the resolution of image attachments
• Refactors the ImageLoading API
• Refactors he ImageCDN with some needed breaking changes
• ComposerVC.addAttachmentToContent() has a new info property (minor breaking change)
• Reorganization of Utils Folder
• Deprecates CGSize.avatarThumbnailSize and moves it to Components.default

🛠 Implementation

• The ImageCDN required breaking changes so that the API is more understandable but also more scalable. The breaking changes are also minimal and will be documented in the changelog.
• In some cases, we know the size of the view where we are loading the image, but in other cases like cells, we don't know, especially in the message list where the message cell can be totally customizable and since the cell is reusable there is no way to get the size upfront unless the view has a static size. So by default, right now the image attachments in the message list have a maximum resolution, if the image attachment goes beyond this limit, it is capped to the maximum resolution which is 2MP (+/- what WhatsApp uses).

🎨 Showcase

Since we are reducing the resolution of the loaded images, the memory footprint reduces a lot. Doing a test with a message list with about 16 images that have high resolution, the memory footprint is reduced by ~6x times.

Before	After

After exporting the memory graph and analysing with VVMap, we can see that especially the Image Raster data is much lower:

Before	After

The reason for these improvements is that for memory use the image resolution is the most important, not the file size. The memory is used by the decoding and decompression of the image which is dependent on the resolution.

For example, if we are talking about an image of 3300x4500, that will be 57MB! For only one image. Since each pixel takes up 4 bytes (if sRGB), we can calculate this with the following formula 3300 * 4500 * 4 / 1024 / 1024 = 56.6MB.

🧪 Manual Testing Notes

• A smoke test around images should be done, although snapshot tests should have found any regression if there was any.

☑️ Contributor Checklist

• I have signed the Stream CLA (required)
• This change follows zero ⚠️ policy (required)
• This change should be manually QAed
• Changelog is updated with client-facing changes
• New code is covered by unit tests
• Comparison screenshots added for visual changes
• Affected documentation updated (docusaurus, tutorial, CMS)

🎁 Meme