The Album tab defines the settings of where and how to store the gallery with all its associated images. Select a folder with write access where you want the gallery to be written to. A sub-folder named KIPIHTMLExport will be created containing everything.
When you check the Resize target images box you can fix the maximum target image size (in pixels) with the slider below it. Images bigger than this value will be scaled down to it, but smaller images will not be modified. The next two check boxes allow you to set specific image compression features. If disk space is of concern check the target image compression and lower the compression level from the host application default value. Then you can choose between JPEG (smallest filesize, but lossy) and PNG (lossless and free license) formats.
If JPEG file format is selected for target resizing images, all EXIF information will be preserved from the original JPEG files.
With the Set different color depth check box you can change the default color depth. This will of course influence the file size. The rest of the settings are rather self-explanatory.