how to edit transparency pixels in a FilterPlugin?

i want develop fiter plugin of photoshop. while not issues:

 

(1) how photoshop provide transparency data ( blank data ) me ?

in other words, want obtain "alpha" channel data, provided "indata" other channels?

 

(2) want change pixel's transparency, means want change totally transparent pixels

 

opaque. how ?

 

 

(3) in pluginname.r file，there 7 entries in filtercaseinfo following. there must pay special attention to?

 

  filtercaseinfo

  {

   {

    /* flat data, no selection */

    inwhitemat, outwhitemat,

    donotwriteoutsideselection,

    filterslayermasks,

    workswithblankdata,

    copysourcetodestination,

 

    ....

 

by way, when invoke filter (i develop 2 yeas ago) on transparency document , photoshop gives messagebox said canot invoke fiter because selection area totally empty.

if area has both transparency , opaque pixels, plugin cause write access faled , made photoshop crash ,  why happen, how avoid it.

 

 

thanks lot.!

first off, don't confuse "alpha" "transparency" different.

 

if create rgb document 1 layer , call dissolve example following bits of information in filterrecord:

 

planes = 4

imagemode = 3 // pluginmodergbcolor

filtercase = 4 // filtercaseeditabletransparencynoselection

inlayerplanes = 3

intransparencymask = 1

 

plane 0 = red, 1 = green, 2 = blue, 3 = transparency

 

see dofilter, loop on planes, , dissolverectangle, changing of data on each plane, in dissolve.cpp example file.

 

now flatten document , create alpha channel , select channels via channels panel. selecing alpha channel or 1 channel have different results.

 

planes = 4

imagemode = 3 // pluginmodergbcolor

filtercase = 2 // filtercaseflatimagewithselection

inlayerplanes = 0

intransparencymask = 0

innonlayerplanes = 4

 

there documentation filtercaseinfo in plug-in resource guide.pdf found in documentation folder.

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