### ImageMagick version

7.1.1-25

### Operating system

Linux

### Operating system, version and so on

Gentoo x86_64

### Description

convert an image to pdf creates a PDF as expected, but the embedded thumbnail is only 1x1 pixel  and does not match the content of the file (white or black image, same-same, pixel is always white)

### Steps to Reproduce

`convert image.jpg image.pdf` 

### Images

[test2.pdf](https://github.com/ImageMagick/ImageMagick/files/14396715/test2.pdf)
![test2](https://github.com/ImageMagick/ImageMagick/assets/32837871/974343e3-ad37-4505-ba37-039704609954)

[regression] converting to PDF does not generate thumbnail properly
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : [regression] converting to PDF does not generate thumbnail properly
Issue date:

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### ImageMagick version

7.1.1-25

### Operating system

Linux

### Operating system, version and so on

Gentoo x86_64

### Description

convert an image to pdf creates a PDF as expected, but the embedded thumbnail is only 1x1 pixel  and does not match the content of the file (white or black image, same-same, pixel is always white)

### Steps to Reproduce

`convert image.jpg image.pdf` 

### Images

[test2.pdf](https://github.com/ImageMagick/ImageMagick/files/14396715/test2.pdf)
![test2](https://github.com/ImageMagick/ImageMagick/assets/32837871/974343e3-ad37-4505-ba37-039704609954)

--- end body ---

None