I want to add or modify a image description of an EXIF image file (EXIF = JPEG plus additional information). After some research I am now able to read and write the image description with the PropertyItem data structure. These PropertyItems are very useful to avoid the bit manipulating in the diabolic file structure of an exif file. But the worse thing is: when writing the image with the changed or new description the picture part becomes recompressed. You can notice this at the file size, you add information to the file and the file size decreases. When you repeat changing the description, the image become more and more poor, because jpg is a lossy compression.
My question is: how do I load and save an jpg or exif file without recompressing the bitmap?