Challenge 3: Why Icons Export as SVG and Photos Export as PNG at Multiple Resolutions — Solution Walkthrough

The answer:

Per this chapter's own material and Vector Graphics' own material on
resolution independence, an icon is typically a clean, simple,
geometric shape — exactly the kind of content a vector format like SVG
represents as mathematical descriptions rather than a fixed pixel
grid. Exporting it as SVG means it displays crisply at any size a real
app might need, on any screen density, without needing separate files
for each size.

Why a photo needs a different approach:

A photo has continuous, irregular tonal detail with no clean
mathematical shape to describe — exactly the case Vector Graphics'
Chapter 1 identified as still genuinely needing a pixel grid. Since a
photo can't be represented as a resolution-independent vector shape in
the first place, it has to be exported as a raster format (PNG or JPG)
at whatever specific pixel resolutions the actual platform needs.

Why photos need multiple resolutions specifically:

Because a raster image's pixel grid is fixed at export time, different
screen densities (1x, 2x, 3x) require separate exported files sized
appropriately for each, unlike an SVG icon, which needs only one
export to look correct everywhere.

WHY THIS WORKS AS AN ANSWER
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This exercise checks that the SVG-for-icons/PNG-for-photos export
choice is correctly traced back to Vector Graphics' own distinction
between resolution-independent vector content and pixel-grid-dependent
raster content.