Why does Invoke-PSImage only output PNG images, and what impact does this have on file size compared to JPEG?

Invoke-PSImage outputs PNG because the payload is stored in the pixel values, and PNG uses lossless compression to preserve that data exactly. JPEG uses lossy compression, which would corrupt the embedded payload. As a result, when a JPEG input is converted to PNG, the output file is typically much larger due to PNG's compression characteristics.