c# - Clarification about how ColorMatrix transformations work -

-

i'm doing work on image processing app (for fun) , struggling understand how colormatrix transformations work. basics of linear/affine transformations, , can fine replicating examples online, i'd grasp why works instead of being satisfied works.

for example, doing simple transformation on image produce negative (each color converted respective complimentary) uses following matrix:

[-1, 0, 0, 0, 0] [0, -1, 0, 0, 0] [0, 0, -1, 0, 0] [0, 0, 0, 1, 0] [1, 1, 1, 0, 1]

i understand -1 cosine of 180degrees, rotation needed "flip" color it's complementary, don't understand how color vector can multiplied against above matrix , produce correct complementary vector.

for instance, if pixel has color vector of [247, 255, 0, 255, 1] (using rgbaw space), performing multiplication against above matrix produces [-247, -255, 0, 255, 1], isn't correct since real complementary color of above [8, 0, 255, 255, 1].

i'm missing obvious here , happy admit i'm not sure i'm doing :) color vector being transformed represented in other coordinate system? (e.g. not 0-255)

if provide "missing link" of understanding, i'd appreciative.

edit

i discovered following matrix works , mathemtically intuitive (it produces correct vector).

-1  0  0  0  0  0 -1  0  0  0  0  0 -1  0  0  1  1  1  1  0  0  0  0  0  1

so new question is: why both of these matrices work? latter 1 provides me more satisfying solution since can grasp why works algebraic perspective. 4 row used scaling? , if so, why scaling add 255? value from?

sorry if these stupid questions, i'm trying down pat.

you correct bottom line translation. hans saying in comment there's scaling factor of 255 involved, what's confusing you. 1 way @ argb values first divided 255, matrix multiplication applied , values multiplied 255 give correct argb values. way @ think of translation values being 255 big. arrive @ same result both ways.

((247/255) * -1 + 1) * 255 = 8 or 247 * -1 + 255 = 8

Comments

Post a Comment

Popular posts from this blog

linux - Mailx and Gmail nss config dir -

-
i trying send mail linux command line using mailx command. can send local domain no problem want set mail send gmail account receive mail sent gmail account. after configuring mail.rc so: account gmail { set smtp=smtps://smtp.gmail.com:587 set smtp-auth=login set smtp-auth-user=username@gmail.com set smtp-auth-password=password set ssl-verify=ignore } i error: resolving host smtp.gmail.com . . . done. connecting 74.125.25.109 . . . connected. missing "nss-config-dir" variable. "/home/username/dead.letter" 11/354 . . . message not sent. after looking "nss-config-dir" here , located certn.db , keyn.db files , added mail.rc so: account gmail { set smtp=smtps://smtp.gmail.com:587 set smtp-auth=login set smtp-auth-user=username@gmail.com set smtp-auth-password=password set ssl-verify=ignore set nss-config-dir=/home/user/.mozilla/firefox/location.default } now when try send mail using command: echo "sent gmail account" | mailx -v -a
Read more

c# - Is it possible to remove an existing registration from Autofac container builder? -

-
something along lines: builder.registertype<mytype>().as<itype>(); builder.registertype<mytype2>().as<itype>(); builder.deregistertype<mytype>().as<itype>() var container = builder.build(); var types = container.resolve<ienumerable<itype>>(); assert.istrue(types.count == 1); assert.istrue(types[0].gettype == typeof(mytype2)); scenario: go through bunch of assemblies , go register types want make sure have 1 implementation of given type. need before create container. track on own nice if autofac me bit. this cannot done directly using containerbuilder , unless start on new one. mind you, having first built container should able construct new container filtering away unwanted types , reusing registrations first container. this: ... var container = builder.build(); builder = new containerbuilder(); var components = container.componentregistry.registrations .where(cr => cr.activator.limittype != typ
Read more

php - Mysql PK and FK char(36) vs int(10) -

-
i have read mysql can handle indexes , searches better if tables keys integers rather char(36) uuid's. is worth converting int(10)? note: use 1 server , have have plans use multiple databases concurrently therefore removing 1 of big reasons using uuid. our tables innodb if makes difference. thanks in advance. usually rdbms can handle integer keys pk more efficient, other datatypes. reason how build index column, yes: long dont require string (or other typed) keys, should use integers. however: char(36) , int(10) far away being equal, because int(10) much smaller, char(36). dont know, if require many different keys, should keep in mind. update, complete last paragraph: int(10) 32-bit, char(36) 36 - ^byte^ (= 288-bit). not mean, int consumes less space, means, char(36) has 4 times more different keys.
Read more