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image cropping on Unity

I've had an issue trying to crop an image in unity. I looked up various methods of tryin to accomplish this but am still pretty new to C# coding. My code is below.
My idea is to use Rectangle information as my cropping tool of the image but it only crops the lower left corner. The goal is to crop a bulk of images and save them back to the folder.
public class ImageCropper : MonoBehaviour
{
[SerializeField] Sprite oldImage;
[SerializeField] GameObject newSize;
//Select a Texture in the Inspector to change to
Texture2D sourceTexture;
RectTransform sourceRect;
private string folder = "**FILEPATH**";
// Start is called before the first frame update
void Start()
{
//Change the Texture to be the one you define in the Inspector
sourceTexture = oldImage.texture;
sourceRect = newSize.GetComponent<RectTransform>();
int x = Mathf.FloorToInt(sourceRect.position.x);
int y = Mathf.FloorToInt(sourceRect.position.y);
int width = Mathf.FloorToInt(sourceRect.rect.width);
int height = Mathf.FloorToInt(sourceRect.rect.height);
/*Debug.Log(sourceRect.position.x + " " + sourceRect.position.y + " " + sourceRect.rect.width + " " + sourceRect.rect.height);
Debug.Log(x + " " + y + " " + width + " " + height);*/
Color[] pix = sourceTexture.GetPixels();
Texture2D newImage = new Texture2D(width, height);
newImage.SetPixels(pix);
newImage.Apply();
byte[] bytes = newImage.EncodeToPNG();
File.WriteAllBytes(folder + "/soldier1.png", bytes);
}
}

Texture2D.GetPixels has an overload that lets you retrieve only a subset of the pixels.
Texture2D Crop(Texture2D sourceTexture, RectTransform cropRectTransform)
{
var cropRect = new RectInt
(
Mathf.FloorToInt(cropRectTransform.position.x),
Mathf.FloorToInt(cropRectTransform.position.y),
Mathf.FloorToInt(cropRectTransform.rect.width),
Mathf.FloorToInt(cropRectTransform.rect.height)
);
var newPixels = sourceTexture.GetPixels(cropRect.x, cropRect.y, cropRect.width, cropRect.height);
var newTexture = new Texture2D(cropRect.width, cropRect.height);
newTexture.SetPixels(newPixels);
newTexture.Apply();
return newTexture;
}

Why would frames drop considerably the longer a Unity Game runs?

I am using Unity 2020.3.4f1 to create a 2D game for mobile.
I created a map builder for the game.
When I hit play, it makes a bunch of 'maps' that are saved as json files. The longer the game plays seems to result in extremely slow frame rates (200fps -> 2 fps) based on the stats menu while the game is running.
The strange thing is if I go to the "Scene" tab and left click on a sprite the fps instantly jumps back up again.
Screenshots
The problem seems related to taking screenshots within Unity.
The big bulge happens & only resets when I un-pause the game.
Questions
Why would the frame rates drop considerably over time the longer the game is running?
Why would the frame rate jump back up after selecting a sprite in the "Scene" tab?
What happens in Unity when selecting a sprite in the "Scene" tab? Is there a garbage collection method?
Script:
private void Awake()
{
myCamera = gameObject.GetComponent<Camera>();
instance = this;
width = 500;
height = 500;
}
private void OnPostRender()
{
if(takeScreenShotOnNextFrame)
{
takeScreenShotOnNextFrame = false;
RenderTexture renderTexture = myCamera.targetTexture;
Texture2D renderResult = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.ARGB32, false);
Rect rect = new Rect(0, 0, renderTexture.width, renderTexture.height);
renderResult.ReadPixels(rect, 0, 0);
float myValue = 0;
float totalPixels = renderResult.width * renderResult.height;
for (int i = 0; i < renderResult.width; i++)
{
for (int j = 0; j < renderResult.height; j++)
{
Color myColor = renderResult.GetPixel(i, j);
myValue += myColor.r;
//Debug.Log("Pixel (" + i + "," + j + "): " + myColor.r);
}
}
occlusion = ((myValue / totalPixels) * 100);
byte[] byteArray = renderResult.EncodeToPNG();
System.IO.File.WriteAllBytes(Application.dataPath + "/Resources/ScreenShots/CameraScreenshot.png", byteArray);
// Cleanup
RenderTexture.ReleaseTemporary(renderTexture);
myCamera.targetTexture = null;
renderResult = null;
}
}
private void TakeScreenshot(int screenWidth, int screenHeight)
{
width = screenWidth;
height = screenHeight;
if(myCamera.targetTexture != null)
{
RenderTexture.ReleaseTemporary(myCamera.targetTexture);
//Debug.Log("Camera target texture null: " + myCamera.targetTexture == null);
}
myCamera.targetTexture = RenderTexture.GetTemporary(width, height, 16);
takeScreenShotOnNextFrame = true;
}
public static void TakeScreenshot_Static(int screenWidth, int screenHeight)
{
instance.TakeScreenshot(screenWidth, screenHeight);
}
}

Different Results Sending Byte Array

Can someone please explain the difference between the 2 examples below:
Pre-build, in Unity, dragging a file (that is renamed from test.jpg to test.jpg.bytes) to a slot defined as a TextAsset (imageAsset) and then using this code:
private byte[] PrepareImageFile()
{
int width = Screen.width;
int height = Screen.height;
var tex = new Texture2D(width, height, TextureFormat.RGB24, false);
tex.LoadImage(imageAsset.bytes);
tex.Apply();
byte[] bytes = tex.EncodeToPNG();
Destroy(tex);
return bytes;
}
Post-build, on an Android tablet, passing in a gallery image path (aPath) then using this code:
private byte[] PrepareTheFile(string aPath)
{
byte[] data = File.ReadAllBytes(aPath);
int width = Screen.width;
int height = Screen.height;
var tex = new Texture2D(width, height, TextureFormat.RGB24, false);
tex.LoadImage(data);
tex.Apply();
byte[] bytes = tex.EncodeToPNG();
Destroy(tex);
return bytes;
}
The reason I know they are different is when the image is sent to a facial recognition API (using bytes), #1 returns accurate results (9/10 identified), but #2 returns inaccurate results (only 1/10 identified correctly).
There are no errors and the image must be reaching its destination for analysis as 1 of the 10 people get identified correctly.
public void GrabImage()
{
NativeGallery.Permission permission = NativeGallery.GetImageFromGallery((path) =>
{
if (path != null)
{
texture = new Texture2D(300, 300, TextureFormat.RGB24, false);
texture.LoadImage(File.ReadAllBytes(path));
Debug.Log(_celebTextAttributes.text + "W:" + texture.width + " x H:" + texture.height);
texture.Apply();
_celebTextAttributes.SetText("Path: " + path);
imagePath = path;
}
}, "Select an image from", "image/png");
_celebImage.GetComponent<Renderer>().material.mainTexture = texture;
}
Any help?

Unity EncodeToPNG saving at 512x512, can't change dimension

I can't seem to get EncodeToPNG() to save to a file dimension other than 512 x 512 even though my texture is 1280 x 1024 which I'm pulling from the dimensions of my RenderTexture object 'tex'. What am I missing? Thank you!
// Saves texture as PNG file.
using UnityEngine;
using System.Collections;
using System.IO;
public class SaveTexture : MonoBehaviour {
public RenderTexture tex;
int tWidth, tHeight;
int getTextureWidth(int texWidth)
{
return tex.width;
}
int getTextureHeight(int texHeight)
{
return tex.height;
}
public void Start()
{
tWidth = getTextureWidth(tex.width);
tHeight = getTextureHeight(tex.height);
Debug.Log("Texture Width: " + tWidth + ", Texture Height: " + tHeight);
}
Texture2D toTexture2D(RenderTexture rTex)
{
Texture2D tex = new Texture2D(tWidth, tHeight, TextureFormat.ARGB32, false);
RenderTexture.active = rTex;
tex.ReadPixels(new Rect(0, 0, tWidth, tHeight), 0, 0);
tex.Apply();
return tex;
}
// Save Texture as PNG
public void SaveTexturePNG()
{
Texture2D myTexture = tex.toTexture2D();
// Encode texture into PNG
byte[] bytes = myTexture.EncodeToPNG();
Object.Destroy(myTexture);
// For testing purposes, also write to a file in the project folder
File.WriteAllBytes(Application.dataPath + "/../AnimalTexture/AnimalTexture.png", bytes);
}
}

I challenged this problem too. Actually there is no problem, file already saved with the resolution you define. On created png's inspector, there is an option named "Advanced->Non-Power of 2". It is selected "ToNearest" as default. Change it to "None" and it will be fixed.

Saving Texture2D to file not working properly

So I've created this class based off of the Texture2D.EncodeToPNG code example on Unity's website. I'm not getting any errors when I execute it, but I'm also not seeing a new file created. What am I doing wrong here?
public class CreateJPG : MonoBehaviour
{
public int width = 1050;
public int height = 700;
string fileName;
string filePath;
// Texture2D tex;
public void GrabJPG () {
SaveJPG();
Debug.Log("GrabJPG Executing");
}
IEnumerator SaveJPG()
{
// We should only read the screen buffer after rendering is complete
yield return new WaitForEndOfFrame();
// Create a texture the size of the screen, RGB24 format
Texture2D tex = new Texture2D(width, height, TextureFormat.RGB24, false);
tex.ReadPixels(new Rect(0,0,width,height),0,0);
tex.Apply();
// Encode texture into JPG
byte[] bytes = tex.EncodeToJPG(60);
Object.Destroy(tex);
// Get filePrefix from GameSetup array index
GameObject init = GameObject.FindGameObjectWithTag("Initializer");
GameSetup gameSetup = init.GetComponent<GameSetup>();
string prefix = gameSetup.filePrefix;
string subDir = gameSetup.subDir;
string dtString = System.DateTime.Now.ToString("MM-dd-yyyy_HHmmssfff");
fileName = prefix+dtString+".jpg";
filePath = "/Users/kenmarold/Screenshots/"+subDir+"/";
Debug.Log("SaveJPG Executing");
File.WriteAllBytes(filePath+fileName, bytes);
Debug.Log("Your file was saved at " + filePath+subDir+prefix+fileName);
if(width > 0 && height > 0)
{
}
}
}

You didn't start your coroutine, you need to call StartCodoutine in GrabJPG:
StartCoroutine(SaveJPG());
https://docs.unity3d.com/Manual/Coroutines.html
https://unity3d.com/learn/tutorials/modules/intermediate/scripting/coroutines
P. S. By the way, you can use Application.CaptureScreenshot