more image info

Author: NicoHinderling

docs/platforms/apple/guides/ios/size-analysis/index.mdx

@@ -30,11 +30,17 @@ description: Upload iOS builds to Sentry for size analysis.
 
 <Include name="size-analysis/build-configuration-ios" />
 
-## App Thinning
+## Understanding App Size
+
+### What We're Measuring
+
+<Include name="size-analysis/what-were-measuring" />
+
+### App Thinning
 
 <Include name="size-analysis/app-thinning" />
 
-## App Store Connect File Sizes
+### App Store Connect File Sizes
 
 <Include name="size-analysis/app-store-connect-file-sizes" />
 

includes/size-analysis/what-were-measuring.mdx

@@ -0,0 +1,15 @@
+Size analysis breaks down compiled files to show you the size contribution of resources and source code.
+
+**Assets**
+Assets such as images, colors and .plist configuration files can come in different variants for different devices. This could be different images for each screen density, or even different configurations depending on the GPU class. If a build is uploaded without first being thinned, you may see multiple copies of your images (ex. different idiom and colorspace values), another reason why we strongly suggest app thinning as a precursor to uploading.
+
+It's also worth noting that storing an image in an asset catalog will allow them to be further compressed. This is why you may see a smaller size for an image in the treemap versus what you might see in your file system.
+
+**Colors**
+Colors are commonly stored in Asset Catalogs to provide different themes for light and dark mode. Individually these have a very small contribution to app size, but together they can add up. If your Asset Catalog contains colors, they will be grouped into a single block that indicates the number of colors in the catalog and the sum of their size contributions.
+
+**Packed Assets**
+Asset Catalogs group similar icons into a compressed format known as a Packed Asset. This is much smaller than storing each icon individually, and is one of the great advantages of Asset Catalogs. However, we won't show you a breakdown of these blocks because the compression applied means there isn't a clear size contribution from each icon.
+
+**Binary**
+Size analysis also breaks down your binary file into logical groups based on their size. If you don't upload dSYMs, or your app is encrypted, we will break the binary into the segments and sections that characterize the file. If you upload a .xcarchive with dSYMs, size analysis will break the binary into individual source files that can be properly attributed to binary size.