How to decrease height of row (with image) in matrix?

The matrix auto-sizes each row to fit the tallest cell content, so the image itself is what is stretching the row. To shrink the row you have to shrink the image inside it.

Open the Format visual pane on the matrix, expand Cell elements, change the "Apply settings to" dropdown to your image column, turn Image size on, and set Height and Width in pixels. Bring those values down until the row looks the way you want.

Also confirm the field feeding the image is set to Data category = Image URL under the Column tools tab, otherwise the Image size options will not appear.

If this helped, a thumbs up and marking it as the accepted solution would be appreciated.

Thanks,

Shai Karmani