An inkjet printer can include an inkjet printhead to print an image on a print medium, and a dryer to reduce or remove moisture from the image. A post-printing treatment fluid can also be present which can include water and a flatness control agent, the flatness control agent including an organic solvent with three or more hydroxyl groups, and a vapor pressure less than 2×10−4 mmHg. A fluid dispenser can be included to apply the post-printing treatment fluid on the print medium after the moisture from the image is reduced or removed. Additionally, the printer can include a mechanical calendering device to apply pressure to the print medium after application and while the print medium is still moistened by the post-printing treatment fluid.