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Add files via upload #30156

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A-n-sh
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@A-n-sh A-n-sh commented Jun 10, 2025 •
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Three-way handler:

                # CHANGE START
                alpha = self.get_alpha()
                if alpha is not None and np.ndim(alpha) > 0:
                    # 2S array a -> pack into 4th channel
                    if A.shape[2] == 3:
                        A = np.dstack([A, alpha])
                    else:
                        A[..., 3] = alpha
                elif alpha is not None:
                    # scalar a -> broadcast or multiply existing
                    if A.shape[2] == 3:
                        A = np.dstack([A, np.full(A.shape[:2], alpha, dtype=A.dtype)])
                    else:
                        A[..., 3] = A[..., 3] * alpha
                # CHANGE END
  1. 2D mask (alpha.ndim>0)
  • RGB input -> stack mask as new 4th channel
  • RGBA input -> overwrite existing alpha channel
  1. Scalar alpha:
  • RGB input -> broadcast into full alpha channel
  • RGBA input -> multiply existing alpha channel by this value
  1. No alpha (alpha is None): leave image's own alpha untouched.

After handling, code premultiplies RGB by updated alpha and resamples-ensuring per-pixel transparency works for both grayscale and RGB images.

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Add files via upload
3998fcf 
Standalone script for isolating issue. Creates a random 10x10 array.
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Thank you for opening your first PR into Matplotlib!

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jklymak commented Jun 10, 2025

Sorry, are you trying to report an issue? A Pull Request is probably not the right way to do that. Please open an issue instead.

@jklymak jklymak added the status: needs clarification Issues that need more information to resolve. label Jun 10, 2025
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A-n-sh commented Jun 10, 2025 via email

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jklymak commented Jun 10, 2025

You didn't fix anything, you just uploaded a file that doesn't do anything.

While we think it is important for students to learn, we don't have the bandwidth to be your class teaching assistants or to walk you though how to make a proper contribution. Please ask your class instructors for help. We also have a very comprehensive development guide that you should read carefully before contributing.

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A-n-sh commented Jun 10, 2025 via email

@jklymak jklymak closed this Jun 10, 2025
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jklymak commented Jun 10, 2025

OK thanks for your interest in Matplotlib, and feel free to resubmit when you have things sorted out.

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