Raw image pixel access
lazarus / 39-Graphics

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user5 · 2019-12-03 22:26

Raw image pixel access is similar to BGRABitmap and in all the
examples of it that I have seen it is used in an xy loop as shown in
the first code example shown below. My question is: Can it be used
outside of an xy loop and if so, how? If possible I would like to use
it in conjunction with some code that opens a text file which provides
xy coordinates such as shown in the second code example. Is this
possible? I've been using TLazIntfImage as shown in the third bit of
code and it's fast but sometimes it occasionally fails and an error
message appears which says "Invalid horizontal index..." or something
like that.


 Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i while
(county < image302.height) do begin  PixelPtr := PixelRowPtr;  while
(countx < image302.width) do   begin    tempcolor := PixelPtr^;   
tempcolor := SwapRedBlue(tempcolor);    Inc(PByte(PixelPtr),
BytePerPixel);    countx := countx + 1;   end;  county := county +
1; end;   while not eof(readfile) do begin  readln(readfile,tempstr); 
val(tempstr,x,code);  readln(readln,tempstr);  val(tempstr,y,code);  
//other code here  end;   while not eof(readfile) do begin 
readln(readfile,tempstr);  val(tempstr,x,code); 
readln(readln,tempstr);  val(tempstr,y,code);   lazimage.colors[x,y]
:= lazcolor;  end;

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winni · 2019-12-03 23:53

Hi!

I show you a solution with BGRAbitmap. I don't know if it exists with
other bitmaps:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i varimg:
TBGRABitmap;i,n : Integer;p.q: PBGRAPixel; beginp := img.data;    for
i := 0 to  img.NbPixels -1 { img.Width * img.Height - 1 } do       
begin         p^ := DoSomething;         inc(p);        end;     
 img.InvalidateBitmap; end; 
But you can access every single pixel by

n := y * Img.width + x;

Then you do

q := p + n;
q^ := clRed;

Winni

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user5 · 2019-12-04 05:25

Hmmmm... Your suggestion is interesting but I don't know much about
TBGRABitmap or if it can be applied to this case. What I have is a
long text file that has information about various pixels in a TImage
which is assigned to a bitmap and then to a TLazIntfImage (or
TBGRABitmap). The number of entries in the text file don't usually
equal the number of pixels in the image.
    Each entry in the text file represents a pixel in the image and
each entry provides x and y. An example of an entry is shown below.
The second line in the sample entry gives a particular color. Lines 5
and 6 respectively provide x and y of the image pixel to be changed.
The 7th line provides another color. The program uses these colors to
produce a third color. The code I'm currently using looks something
like the code shown below following the sample file entry.
    I could have some part of the program count the number of entries
in the file and then use that count number instead of useing while not
eof(readfile). Can you think of a way to apply TBGRABitmap to this
case?
    Thank you so much for helping me. The last few times that I have
asked for help on this forum I received some solutions that were of
critical importance to me.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
 6clWhite3371489418clBlue while not eof(readfile) do //or for i := to
1 to numberofentries do begin  //the program reads each entry in the
text file to get 2 colors along with x and y  //code which uses those
2 colors to produce a third color  lazcolor :=
TColorToFPColor(thirdcolor);  lazimage.colors[x,y] := lazcolor; //the
line that sometimes fails but not always end;

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user5 · 2019-12-04 05:40

Another idea occurred to me. If I can't come up with a way to use
TBGRABitmap in this case then I could put "lazimage.colors[x,y] :=
lazcolor" in a try statement and if it fails then have the program use
"mybitmap.canvas.pixels[x,y] := thirdcolor" instead though this
wouldn't be the best solution.

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user5 · 2019-12-04 06:35

I just realized that my last idea wouldn't work because the code is
working on the TLazIntfImage, not the bitmap. The best that I could do
if it failed would be to just pass up that attempt and then try again.
Duh.

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circular · 2019-12-04 15:57

You can use TBGRABitmap.SetPixel(x,y,color) for that.

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user5 · 2019-12-04 17:59

So the code would be something like this?
    I've had difficulty in installing bgrabitmappackage.lpk in the
past but I'm going to try again.
    Thanks.

    Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var img:
TBGRABitmap;    mybitmap:TBitmap;    x,y:integer;   
tempcolor,thirdcolor:TColor;    readfile:TextFile; begin  mybitmap :=
TBitmap.create; mybitmap.width := image1.width; mybitmap.height :=
image1.height; mybitmap.assign(image1.picture.bitmap); //TImage img :=
TBGRABitmap.create(mybitmap.width,mybitmap.height); img.assign(mybitma
p);  assignfile(readfile,'edges.txt'); reset(readfile);  while not
eof(readfile) do //or for i := to 1 to numberofentries do  begin 
 //the program reads each entry in the text file to get 2 colors along
with x and y   //code which uses those 2 colors to produce a third
color   img.SetPixel(x,y,thirdcolor); 
end;  img.free; mybitmap.free; closefile(readfile); end;

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Handoko · 2019-12-04 18:22

Quote from: user5 on December 04, 2019, 06:59:40 pm    I've had
difficulty in installing bgrabitmappackage.lpk in the past but I'm
going to try again.

Do you know OPM (Online Package Manager)? It makes installing packages
much easier.
https://wiki.freepascal.org/Online_Package_Manager

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user5 · 2019-12-04 18:38

I'm once again having trouble installing bgrabitmappack.lpk
    I downloaded the lpk zip file and unzipped it to a folder
    I clicked on Package and then I clicked on Open Package File
(.lpk)
    I then clicked on bgrabitmappack.lpk
    On the window that appeared I clicked on Use but the only
highlighted item was Add to Project. Install was not highlighted.
    I clicked on Compile but got an error message that said:
C:\Users\Art McGinnis\Desktop\temp9\bgrabitmap-
master\bgrabitmap\bgramultifiletype.pas(70,58) Error: Identifier not
found "RawByteString"
    I don't understand what's going on here. I'm not sure what to do
now. Maybe I'll check out OPM. What a drag.

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user5 · 2019-12-04 19:06

On the OPM page the instructions said: In Lazarus "Install/Uninstall
Packages" window select "OnlinePackageManager" from the available
packages, click "Install selection" and then rebuild the IDE.
    I did that but OnlinePackageManager was not listed as an available
package. I did see an item titled:
LazarusPackageManager 0.0.1 and I tried to install it but got an error
message that said: Broken dependency - Ome or more required packages
were not found.
    If someone could provide me with step by step instructions then
that might help.
    Otherwise I guess that I can't use BGRABitmap.

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Handoko · 2019-12-04 19:13

Don't give up easily sir.

What is the version of your Lazarus? OPM can be found in the
directory:
($LazarusDir)/components/onlinepackagemanager

But if you can't find it (because you're using older Lazarus version),
you can download OPM 1.6 from here:
https://drive.google.com/file/d/0B9Me_c5onmWobVZOdVlXSlZRRmc/view

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circular · 2019-12-04 22:29

You don't need to install BGRABitmap. Just open the package once and
that's it.

After that, you can add it to your project.

https://wiki.freepascal.org/BGRABitmap_tutorial_1

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user5 · 2019-12-04 22:30

Yes, you are correct; I had forgotten that I was using an older
version of Lazarus because a project I was trying to use wouldn't
compile with the newest version of Lazarus.
    I uninstalled the old version and installed the new version of
Lazarus. I installed the component for OPM and then used it to install
BGRABitmap.
    The code img.SetPixel(x,y,thirdcolor); compiled just fine so it
looks like I'm in business.
    Thank you all for your patience and understanding. Once again this
forum came through for me.

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circular · 2019-12-04 22:33

You're welcome