Sorry for the long post, but I think that the issue needs some discussion.
I wrote to this group several days ago about the larger PDF file output sizes when using 1.7.1 vs 1.6.0. I have done some work and discovered that the observation of larger PDF output files happened between 1.6.0 and 1.7.0. I was incorrect in suggesting that the problem was with 1.7.1. I tried some testcases and discovered that a study of the source was needed. Turns out that the issue may not really be a "bug" but more of a "feature". However the lack of consistency (and documentation?) has caused some of the problems I've encountered. There are 2 obvious ways to instantiate the PDJpeg object, one with a FileInputStream, and other with a BufferedImage. With the FileInputStream instantiation, everything looks the same between 1.6.0 and 1.7.0. Files are the same size. I cannot use this instantiation for my project, because I have both monochrome (gray-scale) and color images. The FileInputStream code sets all images as color, and that causes the PDF readers to choke. Some throw an error, others just won't display the gray-scale image. To get around that behavior, I changed my production code to use the BufferedImage instantiation. Apparently, with version 1.7.0, the PDFBox code checks for gray-scale vs color, and sets the correct parameters. This is a good thing, and removes my work-around. However, the larger PDF files I was observing were due to a change in the handling of the quality (compression) level of the JPG files so instantiated. The execution pathways for these two instantiation methods are quite different, and this leads to different behavior between the two. One obvious difference I have already described, as being the setting of the correct gray vs color parameter. The other differences very much involve the JPG quality setting. More quality; larger PDF files (about 3x the size under 1.6.0). In addition, there is a "compression" parameter used in PDJpeg (or which can be specified in the constructor) that is not passed onwards to the image writer in 1.7.0. It appears to be a dead-end value. The BufferedImage constructor seems to be setting the quality to 1.0, while the previous system appears to have set it to 0.75. These quality differences may explain the larger output files. However, there seems to be no way to set the quality explicitly. The image writer now used in 1.7.0 (ImageIOUtil.writeImage), in addition, is invoked with no "resolution" parameter, and thus seems to arbitrarily set a 72dpi resolution for the images. I do not understand the function of this "resolution" entry. Can someone explain it? Is it important? Were there changes to the JavaDoc to explain the settings for these two methods of instantiation for PDJpeg? Unfortunately, I seem to have mislayed the link for the JavaDoc for PDFBox 1.7.1. The "bottom line" may be that there are no guide-lines that I know of, for which instantiation to use for PDJpeg. I have no information on the other settings, such as the "resolution", and the "quality" of the JPG files has been set to a specific value, with no mechanism to alter it (not necessarily a bug?). [Part of the reason for asking the above questions, is that I need the illustrations to be good enough to be zoomed in closely, when a user reads the book with a reader such as Acrobat. If I create what I hope are good-quality JPG's, but the final image looks poor when zoomed in, then all the extra work is wasted.] Thanks, as always for all the good work that has gone into PDFBox. Bob Swanson
