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Get amount of unique colors from picture
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Author
Topic: Get amount of unique colors from picture (Read 2297 times)
lulZghost
Guest
Get amount of unique colors from picture
«
on:
October 16, 2018, 03:34:39 pm »
For my project I need a function way to get the amount of unique colors from a single picture.
My Idea was to make an array of strings, go pixel by pixel, convert the color to string, check if the string already exists and if not add it to the array.
This is my code for it:
Code: Pascal
[Select]
[+]
[-]
private
colorlist
:
array
of
string
;
---------------------------------
function
TFormMain
.
checkColors
(
)
:
integer
;
var
i
,
x
,
y
,
doesexist
:
integer
;
colorstring
:
string
;
begin
for
y
:
=
0
to
image1
.
canvas
.
Height
do
begin
for
x
:
=
0
to
image1
.
canvas
.
Width
do
begin
colorstring
:
=
ColorToString
(
FPColorToTColor
(
image1
.
Canvas
.
Colors
[
x
,
y
]
)
)
;
for
i
:
=
0
to
length
(
colorlist
)
do
begin
doesexist
:
=
0
;
if
colorlist
[
i
]
=
colorstring
then
doesexist
:
=
1
;
end
;
if
doesexist
=
0
then
begin
SetLength
(
colorlist
,
Length
(
colorlist
)
+
1
)
;
colorlist
[
High
(
colorlist
)
]
:
=
colorstring
;
end
;
end
;
end
;
result
:
=
length
(
colorlist
)
;
end
;
SO, apparently this doesn't work, because I get this error
Code: Pascal
[Select]
[+]
[-]
000000010000AC15 668b41e8 mov
-
0x18
(
%rcx
)
,
%ax
I don't get any syntax errors, so somewhere I have another error, but I don't see it. Maybe someone else can spot the logic error in there, because I honestly don't know what the error could be.
Logged
marcov
Administrator
Hero Member
Posts: 11455
FPC developer.
Re: Get amount of unique colors from picture
«
Reply #1 on:
October 16, 2018, 03:35:58 pm »
Code:
[Select]
for i:=0 to length(colorlist) do
Iterates over length(colorlist)+1, is this really what you want?
Also, as a rule, don't convert to string what is not a string.
Logged
Blaazen
Hero Member
Posts: 3241
POKE 54296,15
Re: Get amount of unique colors from picture
«
Reply #2 on:
October 16, 2018, 04:31:36 pm »
I would allocate array with size 256*256*256/8 = 2MB, it will cover RGB values from (0,0,0),(0,0,1)...(255,255,254),(255,255,255) and each bit represents color: 0..not present, 1..present. In the end you can only do sum of "1" bits.
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Lazarus 2.3.0 (rev main-2_3-2863...) FPC 3.3.1 x86_64-linux-qt Chakra, Qt 4.8.7/5.13.2, Plasma 5.17.3
Lazarus 1.8.2 r57369 FPC 3.0.4 i386-win32-win32/win64 Wine 3.21
Try Eye-Candy Controls:
https://sourceforge.net/projects/eccontrols/files/
LemonParty
Jr. Member
Posts: 63
Re: Get amount of unique colors from picture
«
Reply #3 on:
October 19, 2018, 10:57:56 am »
Using strings for such purpouses is ineffective.
Blaazen's idea is really good.
Use
https://www.freepascal.org/docs-html/rtl/system/popcnt.html
to count the number of setted bits.
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Get amount of unique colors from picture
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