Here's the test I ran:
- Set up an HTML upload on my server. It simply stores a file byte-for-byte.
- Uploaded a JPEG image via a PC. Call this original.jpg
- Downloaded that JPEG from the server via iPhone Safari.
- Used the Mail app to send a copy to a Yahoo email. Call this one mailed.jpg
- Uploaded the same image from the iPhone to the HTML form with Safari. Call this safariupload.jpg
- Uploaded the same image again, this time with Chrome. This is chromeupload.jpg
- Upload the image to DropBox via the dropbox app. This is dropbox.jpg
- Using Irfanview's JPG Lossless Operations plugin, I optimized all 5 JPEGs and stripped all EXIF info.
- Did a byte-wise compare on all 5 images. original.jpg, mailed.jpg, and dropbox.jpg were identical, however both safariupload.jpg and chromeupload.jpg have a larger filesize and show signs of recompression.
This test was conducted over WiFi.
It would seem that anytime the iPhone uploads an image to an HTML form, regardless of which app is used, it re-compresses the image.
Has anyone else experienced this? Is there a solution?