>I have a table (SQL) that contain many pictures.
>The pictures source is BMP format (RGB but the content is gray scale).
>Each picture is about 650 kb.
>How can I minimize the picture size by VFP with/without changing the format (and to change it to grayscale).
>In addition, this change will change the print quality?

AFAIK, there is no built-in means to convert images in VFP. But this could be done by external application or control.

The size of BMP can be changed only by reducing number of used colors.
For example, converting from truecolor (32 or 24 bit) to highcolor (16 bit) will reduce the file size on 2 or 1 byte per each pixel adequately. Conversion to indexed colors (256 or even 16 colors) will result reduce the size more but may corrupt image quality depending on how many colors are really used on image. For example, 265 colors is good enough for document or plot but bad for fotos. I also recommend to use

As for other foormats, JPEG is very good for fotos. It slightly reduces image quality but gives huge reduce in file size compered to BMP and thus is used everywhere for images like fotos.
GIF and PNG have indexed numbers of colors and are better than BMP for documents or small fotos but cannot be used for large images with deep color transitions.