Daniel Mitchell wrote:
I'm curious about how your library communicates the type of pixel data
contained in an image.
I presume you need to know so you know what type of image to give it? There are three scenarios: 1. If you know what channel type and color space the image on disk is, you can use jpeg_read_image passing it an image of the right color space / channel. If you are wrong an exception is thrown. (You don't have to get the channel permutations correct by the way - you can read an rgb image into a bgr destination) 2. If you don't know the image format on disk is but you just need the image in a specific color space and channel depth, you can use jpeg_read_and_convert_image passing it the type of image that you need. As long as color space and channel depth conversion is provided between the source and target color space and channel depth, this will read the image and color convert. It does it on the fly (doesn't need to store the image data and then color-convert) 3. If you don't know the image format on disk and you want to read the image in its native color space and channel depth, you must use jpeg_read_image passing it a run-time specified image (any_image). The I/O code will try to match the image on disk with any of the allowed types of your run-time image (as always, channel permutations are ignored) and if a match is found it will read and instantiate the image in that format. If none of the allowed image types of your any_image is a match it will throw an exception. For all of the above, instead of images you can use views (templated or any_image_view). The calls are jpeg_read_view, jpeg_read_and_convert_view. Using a view transformation, this allows you to do some very powerful things, like fetch a subimage of your large image from disk (using subimage_view) or read the image upside down, etc, all without using any extra memory and without copying the data. Image views don't own the pixels. Loading into a view will not allocate extra memory. However, the dimensions of your image on disk must match that of the view or else an exception is thrown. All of the above apply for TIFF and PNG, just replace jpeg_ with tiff_ and png_ Lubomir