Oh, I see. And now I can understand what the code mean. But the question is that the same picture but different size would output different result, for e.g, use this picture( http://www.tophdwallpaersland.com/wp-content/uploads/2015/01/windows-desktop-widescreen-backgrounds.jpg) as the desktop, when used the resolution 1920×1080, clicked refresh and then I got the result is BITMAP_GRADUAL_MEDIUM from `_get_bitmap_graduality_level`, (of curse, there is some optimization so that the size of bitmap is 1920×1050, no 50 px for taskbar), but used the resolution 1024×768 (actually is 1024×738), refreshed and then I got the result is BITMAP_GRADUAL_HIGH and it means using jpeg compress. I think the key point is these two macro CONTRAST_TH and ADMPLE_JUMP in server/red_bitmap_utils.h which result in same picture but different BitmapGradualType. Or using the OpenCV calculating the histogram to judge the image ? 2016-04-25 21:01 GMT+08:00 Frediano Ziglio <fziglio@xxxxxxxxxx>: >> >> Hi, I'm a beginner at SPICE project. Today, I was reading the code, >> the function which named `_get_bitmap_graduality_level` at line 5979 >> in file server/red_worker.c (the version of spice is 0.12.7 and my OS >> is Fedora 23). It seems that get a score value from a image by the >> function and I also found the function `void >> FNAME(compute_lines_gradual_score)` at line 116 in file >> server/red_bitmap_utils.h. I really can't understand the what these >> two functions do, the logic, I mean. >> >> So the question is that could you tell me the principle of the >> algorithm? thanks : ) > > Basically try to detect if a picture is a natural one or a result of > a draw. > Natural picture are better to be compressed with some algorithms (like > jpeg). > The idea is that you take some samples in the image and score based on > the variation (let's say for instance the color change less that 20% > from a pixel to the next you score 1 otherwise you score 0). > > Frediano _______________________________________________ Spice-devel mailing list Spice-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/spice-devel
