ch2 image fixes

ch02.asciidoc

@@ -28,6 +28,7 @@ image::images/Bitcoin_Overview.png["Bitcoin Overview"]
 
 Alice, who we introduced in the previous chapter, is a new user who has just acquired her first bitcoin. In <<getting_first_bitcoin>>, Alice met with her frined Joe to exchange some cash for bitcoin. The transaction created by Joe, funded Alice's wallet with 0.10 BTC. Now Alice will make her first retail transaction, buying a cup of coffee at Bob's coffee shop in Palo Alto, California. Bob's coffee shop recently started accepting bitcoin payments, by adding a bitcoin option to his point-of-sale system (see <<bitcoin_for_merchants>> for information on using bitcoin for merchants/retail). The prices at Bob's Cafe are listed in the local currency (US dollars) but at the register, customers have the option of paying in either dollars or bitcoin. Alice places her order for a cup of coffee and Bob enters the transaction at the register. The point-of-sale system will convert the total price from US dollars to bitcoins at the prevailing market rate and displays the prices in both currencies, as well as showing a QR code containing a _payment request_ for this transaction:
 
+.Displayed on Bob's cash register
 ----
 Total:
 $1.50 USD
@@ -36,7 +37,7 @@ $1.50 USD
 
 [[payment-request-QR]]
 .Payment Request QR Code - encodes a payment request URL as defined in BIP0021
-image::images/payment-request-qr.gif["payment-request"]
+image::images/payment-request-qr.png["payment-request"]
 
 [[payment-request-URL]]
 .The payment request QR code above encodes the following URL, defined in BIP0021