Trying to Crop an Image on iOS and some Android devices and returns with wrong position

Questions & Answers
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1

Hello,

I have this piece of code that crops an image and works well in the editor and android, but for some reason in iOS and some Android devices it shows a wrong position. Anyone know why this happen? I saw that RenderTexture have some bugs in the past but I don’t know exactly what is happening

private IEnumerator CropImage(Texture original, int width, int height)
{
    yield return new WaitForEndOfFrame();

    float originalWidth = original.width;
    float originalHeight = original.height;
    float originalAspectRatio = originalWidth / originalHeight;
    float targetAspectRatio = (float)width / (float)height;
    float scaleFactor;
    if (originalAspectRatio >= targetAspectRatio)
    {
        // Image is wider than frame. Use height to determine scale.
        scaleFactor = height / originalHeight;
        Debug.Log("[Image Editor]: Image is wider than frame. Scale Factor: " + scaleFactor);
    }
    else
    {
        // image is taller than frame. Use width to determine scale
        scaleFactor = width / originalWidth;
        Debug.Log("[Image Editor]: Image is taller than frame. Scale Factor: " + scaleFactor);
    }

    int newWidth = Mathf.FloorToInt(originalWidth * scaleFactor * _zoomScale);
    int newHeight = Mathf.FloorToInt(originalHeight * scaleFactor * _zoomScale);

    RenderTexture rTex = new RenderTexture(newWidth, newHeight, 24, RenderTextureFormat.ARGB32);
    Graphics.Blit(original, rTex);

    Texture2D newTex = new Texture2D(width, height, TextureFormat.RGB24, false);
    RenderTexture.active = rTex;

    Vector2 imagePositions = m_Image.rectTransform.localPosition;
    float xPos = (newWidth - width) * 0.5f - imagePositions.x;
    float yPos = (newHeight - height) * 0.5f + imagePositions.y;

    newTex.ReadPixels(new Rect(new Vector2(xPos, yPos), m_Image.rectTransform.rect.size), 0, 0);
    //newTex.ReadPixels(new Rect(xPos, yPos, ImageContainer.rect.width, ImageContainer.rect.height), 0, 0);
    yield return new WaitForEndOfFrame();

    newTex.Apply();
    finalTex = newTex;
    m_CroppedImage.texture = finalTex;
    _data.OnSetImage?.Invoke(finalTex);
    UIManager.Inst.RemoveTopModal();
}
2

Are you sure your xPos and yPos are positive? You can not read information from say -12. Maybe your display is too small? Start debugging the values you actually use in ReadPixels. I didn’t go through all of your logic. However if you want to down / upscale the actual image and crop the edges (either top and bottom or left and right), why do you involve that m_Image here?

Usually you would calculate the offset from the cropping parameters. You may have a look at my code over here. It actually resamples the image to a desired size and makes sure it fills the target space cropping as necessary. I also have a letter / pillar box version in my linked TextureTools.cs.

3

SOLVED.
I already found the issue, and I was right when I say that provides of the Graphics API. Thanks to Bunny to help me realize that. I had to verify which Graphics API I using

If you have something more clean to verify this please share with me.

float xPos = ((newWidth - width) * 0.5f) - ImageContainer.anchoredPosition.x;
float yPos = ((newHeight - height) * 0.5f) + ImageContainer.anchoredPosition.y;

if (SystemInfo.graphicsDeviceType == UnityEngine.Rendering.GraphicsDeviceType.OpenGLCore || SystemInfo.graphicsDeviceType == UnityEngine.Rendering.GraphicsDeviceType.OpenGLES2 || SystemInfo.graphicsDeviceType == UnityEngine.Rendering.GraphicsDeviceType.OpenGLES3 ||SystemInfo.graphicsDeviceType == UnityEngine.Rendering.GraphicsDeviceType.Metal)
{
    yPos = ((newHeight - height) * 0.5f) + (1 - ImageContainer.anchoredPosition.y);
}