The picture you drew is just how I imagined my birthday party would be!
This is just what I thought my birthday party would look like!
ーThe picture you drew is just how I imagined my birthday party would be!
「あなたが描いてくれた絵はまさに私が想像した誕生日パーティーです!」
... is just how I imagined ~ で「…はまさに私がイメージした通りの〜です」
ーThis is just what I thought my birthday party would look like!
「これはまさに私が思った通りの誕生日パーティーです!」
This is just what I thought ... で「これはまさに私が思った通りの…です」
ご参考まで!