I am working with a a 2 plane char matrix and trying to convert pix to world range inside matrix land.

[jit.expr @expr "(in[0].p[0] / 320.)*2. -1." "(in[0].p[1] / 240.)*2. -1."]

I can't get results with this expr:
[jit.expr @expr "(in[0].p[0] / 320.)*2. -1." "(in[0].p[1] / 240.)*2. -1."]

jit-expr-issue

not sure exactly what you are trying to do.

the char matrix is spitting out values between 0 and 255. if you want to convert that to float, between 0. and 1., simply convert the type of the matrix to float32:

jit.expr 2 float32 4 1 @adapt 0 @expr in[0] in[0]

looks like maybe you want 0 255 to -1 to 1:

jit.expr 2 float32 4 1 @adapt 0 @expr (in[0]*2)-1 (in[0]*2)-1

not sure why you have 320 and 240 so maybe you can explain more what you're trying to achieve.

not sure exactly what you are trying to do.
the char matrix is spitting out values between 0 and 255. if you want to convert that to float, between 0. and 1., simply convert the type of the matrix to float32:

not sure why you have 320 and 240 so maybe you can explain more what you're trying to achieve.


Sorry, there was an error in my statement.

Yes, of course a char matrix goes up to 255.

I was trying to convert float32 matrix filled with values between 0-320. for plane 0 and 0-240 for plane 1 to world coordinates.

However I'd like now to tell my expr to convert plane 1 from 0. 240. to 1. -1. not -1. 1.

My patch allows to sort elmts from cv.jit.sort and fill a new matrix without "cell-jump".

Sorry, there was an error in my statement.
Yes, of course a char matrix goes up to 255.

I was trying to convert float32 matrix filled with values between 0-320. for plane 0 and 0-240 for plane 1 to world coordinates.
That is good now.

I tryed 
(-in[0].p[1] / 240.)*2. -1.
(in[0].p[1] / -240.)*2. -1.

But is there a reason for [jit.expr] does'nt accept the "" in my second expression?

Other, I discovered that exprfill message to [jit.matrix] do not work as expr message do with [jit.expr].

I thought that they both would work the same way? But no?

It would be nice to have clarifications with expression syntaxe and features.

A special tutorial somewhere would be nice.

Other, I discovered that exprfill message to [jit.matrix] do not work as expr message do with [jit.expr].
I thought that they both would work the same way? But no?

It would be nice to have clarifications with expression syntaxe and features.
A special tutorial somewhere would be nice.


Writing an in-depth jit.expr/exprfill tutorial has been on my "Todo Someday" list for some time now. Some of the later Jitter Recipes in Book 3 make use of it to draw geometry.

For your particular problem, exprfill can't understand the "in[0]" because, well the exprfill is a one time action on a jit.matrix. If you need a dynamic expression with inputs, you are better off using jit.expr.

Also, if you want to fill different planes with different expressions, you need to use separate exprfill messages with a plane argument before the expression, i.e. (exprfill 0 snorm[0],exprfill 1 snorm[1]).

Writing an in-depth jit.expr/exprfill tutorial has been on my "Todo Someday" list for some time now.  Some of the later Jitter Recipes in Book 3 make use of it to draw geometry.

indeed, it would be fantastic to have a jit.expr tutorial as it is one of the most powerful objects within jitter. Please keep us informed if it happens!

jit.expr issue