could you explain to me how size parameter from read function- http://www.graphicsmagick.org/Magick++/Image.html#read could be used? Does it give a possibilty to do some scaling during load of image from file? Is it dependant on file type?
I have made some tests with quite big png and jpeg files and results were not consistent, so probably I missed something and read function with specified size doesn't work as I have supposed.
Maybe there is some example out there, that could clarify this?
The size hint only has an effect for JPEG files. It depends on functionality in the JPEG library and uses features specific to the JPEG format. PNG format is not a multi-resolution format so it is necessary to read all of the data from the PNG and scale it. If image resize is a problem, then look for the thumbnail() and scale() methods which work best for large images.
Thank you very much for a clarification and hint!