A printing system having an image supply device and a printer, for printing an image with the printer based on image data supplied from the image supply device, wherein the image supply device comprises: means (S3, 3110) configured to obtain function information of the printer upon communication between the image supply device and the printer; means (S4, 2700) configured to establish a print setting window based on the function information and displaying the print setting window; job generation means (S7, 3100) configured to generate a print job based on print conditions set via the print setting window; job transmission means (S8, 3110) configured to transmit the print job to the printer; reception means (S9, 3110) configured to receive a request for file information of an image file from the printer, wherein the request for file information contains a request for file information of a first image file to be printed designated by the print job; conversion means (S10, 3100) configured to convert image data of the first image file to be printed according to the set print conditions, and configured to generate a second image file including the image data of the first image file that has been converted, wherein the conversion means is arranged to start conversion of the first image file in response to the request for file information received by the reception means; first transmission means (S11, 3110) configured to transmit the file information of the second image file, but not the file information of the first image file as requested in the request for file information, to the printer in response to the request received by said reception means; and second transmission means (S13, 3110) configured to transmit the second image file to the printer in response to a file request received from the printer after transmitting the file information to the printer, wherein the printer is arranged to print an image based on the second image file transmitted by said second transmission means. means (S3, 3110) configured to obtain function information of the printer upon communication between the image supply device and the printer; means (S4, 2700) configured to establish a print setting window based on the function information and displaying the print setting window; job generation means (S7, 3100) configured to generate a print job based on print conditions set via the print setting window; job transmission means (S8, 3110) configured to transmit the print job to the printer; reception means (S9, 3110) configured to receive a request for file information of an image file from the printer, wherein the request for file information contains a request for file information of a first image file to be printed designated by the print job; conversion means (S10, 3100) configured to convert image data of the first image file to be printed according to the set print conditions, and configured to generate a second image file including the image data of the first image file that has been converted, wherein the conversion means is arranged to start conversion of the first image file in response to the request for file information received by the reception means; first transmission means (S11, 3110) configured to transmit the file information of the second image file, but not the file information of the first image file as requested in the request for file information, to the printer in response to the request received by said reception means; and second transmission means (S13, 3110) configured to transmit the second image file to the printer in response to a file request received from the printer after transmitting the file information to the printer, wherein the printer is arranged to print an image based on the second image file transmitted by said second transmission means.