Actually, I think we missed a very important point at the beginning. Saving PDF pages to an image almost always causes severe quality losses that are nothing to do with compression. Here's why.
A PDF is a mixture of some or all of:
- text
- vector art (shapes, lines, etc.)
- raster images (originally TIFF, JPEG or whatever) at DIFFERENT resolutions
Now, if you save a page of a PDF to a raster format, then what happens to the above is:
- text must be converted to a raster format. It is no longer text, free to scale and sharp to read at anysize
- vector art must be conveted to a raster format with similar losses to text
- raster images have to be converted to the final resolution. Unless the resolution of the image and of the exported graphic happen to be the same there will be quality losses
So, whether you choose JPEG, PNG or whatever, it is only in a very small set of circumstances lossless. That is, when the PDF contains nothing but raster images, all at the same resolution, which is the same as the exported resolution.
