Image forming apparatus

An image forming apparatus, comprising:

• an ink container;
• a subtank with which ink from the ink container is replenished;
• an ink replenishment path from the ink container to the subtank;
• a head configured to eject the ink supplied from the subtank in accordance with a printing image;
• a container residual amount sensor configured to detect ink empty of the ink container;
• an ink consumption estimating unit configured to derive an ink consumption estimation value from image data of the printing image;
• and
• a control unit configured to (a) set an ink residual amount estimation value of the subtank as a first reference value corresponding to a tank capacity of the subtank when ink empty is detected on the ink container, and determine whether the ink residual amount estimation value is less than the ink consumption estimation value of a subsequent page in a print job or not, and (b1) stop the print job if the ink residual amount estimation value is less than the ink consumption estimation value of the subsequent page and (b2) continue the print job if the ink residual amount estimation value is equal to or larger than the ink consumption estimation value of the subsequent page,
• wherein the control unit renews the ink residual amount estimation value with a value obtained by subtracting the ink consumption estimation value from the ink residual amount estimation value if the ink residual amount estimation value is equal to or larger than the ink consumption estimation value of the subsequent page and the print job is continued, and determines whether the renewed ink residual amount estimation amount is less than the ink consumption estimation amount of a next print job or not when the next print job is performed, (c1) does not perform the next print job if the renewed ink residual amount estimation amount is less than the ink consumption estimation amount of the next print job, and (c2) performs the next print job if the renewed ink residual amount estimation amount is equal to or larger than the ink consumption estimation amount of the next print job.