Create a png image from a string
lazarus / 39-Graphics

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PepperJules · 2025-07-09 15:32

I have difficulties to find out where to start, and I hope some of you
experienced coders can point
me in the right direction...

I have a variable containing a string, and would like to create a png
image from it.
I would like to be able to set the text font, text color and text
size, as well as the background color
of the image (black, white or alpha).

The image file format can also be jpg.

What units/components should I be looking at?
Platform = windows

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thijsvandien · 2025-07-09 16:53

Forget about the final image format for now. As long as you can
produce a bitmap (basically a grid of pixels), it can later be
converted to something more efficient. JPEG doesn't support
transparency, however.

Here's an intro:
https://wiki.freepascal.org/Developing_with_Graphics

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jamie · 2025-07-09 21:56

There are some considerations you must examine.

 You do not indicate if this string variable is to be used over the
network, so that would mean not using upper 128 chars?

 You have a choice of using a encoding 64 functions as such.

 a human readable string would mean encoding the image into a Hex
string, which will make it twice the size but at least if can be
contained in a string without issues.


 You need to specify more details!

Jamie

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TBMan · 2025-07-09 22:55

Quote from: PepperJules on July 09, 2025, 05:32:46 pmI have
difficulties to find out where to start, and I hope some of you
experienced coders can point
me in the right direction...

I have a variable containing a string, and would like to create a png
image from it.
I would like to be able to set the text font, text color and text
size, as well as the background color
of the image (black, white or alpha).

The image file format can also be jpg.

What units/components should I be looking at?
Platform = windows

It sounds like you want to learn how to code run-length encoded image
files.
*OR

You want to save current display options in a program which is
different.

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H₂SO₄ · 2025-07-10 05:05

Here's a very barebones example program that creates an image, draws
some text on it, and saves it as a  .png:

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 program
Example; {$mode objfpc}{$H+} uses  Interfaces, Graphics; procedure
DrawExample(const Text: String);var  Image: TPicture;begin   // Create
blank 256 x 256 image  Image := TPicture.Create(); 
Image.PNG.SetSize(256, 256);   // Draw something using the canvas 
with Image.PNG.Canvas do begin     // Fill background color   
Brush.Color := TColor($F7F4F0);    Brush.Style := bsSolid;   
FillRect(0, 0, Image.Width, Image.Height);     // Draw text   
Font.Color := clTeal;    Font.Name := 'Arial';    Font.Height := 48; 
 TextOut(16, 96, Text);  end;   // Save & destroy image 
Image.SaveToFile('test.png');  Image.Free();end; begin 
DrawExample('Hello World!');end.
Code: Bash  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i fpc
example.pas ^    -FuC:\lazarus\lcl\units\x86_64-win64 ^   
-FuC:\lazarus\lcl\units\x86_64-win64\win32 ^   
-FuC:\lazarus\components\lazutils\lib\x86_64-win64
If you want to do anything involving transparency that is more
complicated than filling non-antialiased rectangles (i.e. pretty much
anything), I'd encourage you to switch to BGRABitmap; it's a household
name in the Free Pascal / Lazarus ecosystem and has lots of features,
although its documentation is a bit lacking.

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Boleeman · 2025-07-10 05:29

And a Text on Paintbox example.

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paweld · 2025-07-10 10:57

or BGRABitmap:
https://forum.lazarus.freepascal.org/index.php?topic=48431.0
https://wiki.freepascal.org/BGRABitmap_tutorial_12