On 1/29/23, Michael Koch <astroelectro...@t-online.de> wrote: > Am 29.01.2023 um 23:07 schrieb Paul B Mahol: >> On 1/29/23, Michael Koch <astroelectro...@t-online.de> wrote: >>> Am 29.01.2023 um 22:05 schrieb Paul B Mahol: >>>> On 1/29/23, Michael Koch <astroelectro...@t-online.de> wrote: >>>>> Am 29.01.2023 um 19:32 schrieb Paul B Mahol: >>>>>> On 1/29/23, Michael Koch <astroelectro...@t-online.de> wrote: >>>>>>> Hello, >>>>>>> >>>>>>> if I understood the documentation correctly, the normalize filter >>>>>>> maps >>>>>>> the darkest input pixel to blackpt and the brightest input pixel to >>>>>>> whitept: >>>>>>> darkest pixel --> blackpt >>>>>>> brightest pixel --> whitept >>>>>>> >>>>>>> However I need a slightly different mapping: >>>>>>> A black input pixel shall remain black, and the brightest input >>>>>>> pixel >>>>>>> shall become white. >>>>>>> black --> blackpt >>>>>>> brightest pixel --> whitept >>>>>>> >>>>>>> With other words: Just multiply all pixels by a suitable constant. >>>>>>> Don't >>>>>>> add or subtract anything. >>>>>>> Is this possible? >>>>>>> >>>>>>> Known workaround: Make sure that the input frame contains a black >>>>>>> pixel, >>>>>>> by inserting one in a corner. >>>>>> Try attached patch. >>>>> How must I set the options for the desired behaviour? >>>> Set first strength to reverse of second strength. >>>> So 1.0 and 0.0 or 0.0 and 1.0 >>> I did try with strength=0:strength2=1 but the output isn't as expected. >>> >>> I'm using this input image: >>> http://www.astro-electronic.de/flat.png >>> >>> The pixel values are about 171 in the center and 107 in the top right >>> corner. >>> The center to corner ratio is 171 / 107 = 1.6 >>> >>> In the output image I measure 248 in the center (which is almost as >>> expected, probably correct because I'm measuring the average of a 7x7 >>> neighborhood), but I measure 122 in the top right corner. >>> The center to corner ratio is 248 / 122 = 2.03 >>> The corner is too dark. >>> >> I checked with oscilloscope filter (s=1:tw=1:t=1:x=0), far left pixels >> (as they are darkest) and they are not changing (min values are same >> with and without filter run) >> With default parameters and just strength(2) set to your values, so >> the darkest pixels are left untouched. Did not checked brightest >> pixels output, but they should be correct too. > > But that's not the behaviour I need. All pixels shall be multiplied by > the same suitable constant, so that the brightest pixel becomes white. > > Input center: 171 > Input corner: 107 > > constant c = 255 / 171 =1.49 > Output center: 171 * c = 255 > Output corner: 107 * c = 160 >
Normalization does not do that and that functionality does not belong to such filter, it stretches ranges of all pixel values so they reach maximal possible range. _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
