Enhancement: use density provided to withMetadata as fallback value for TIFF xres/yres #2941
Description
What are you trying to achieve?
Set a specific density/resolution on an output image. (I realize this changes nothing inherent about the image, but some of our users are getting confused by the default print dimensions of an image based on its stored resolution and I'd like to make the problem go away.)
Have you searched for similar questions?
Yes. Other questions/issues have come close, but haven't quite addressed the difference between output formats when it comes to metadata and density.
Are you able to provide a minimal, standalone code sample that demonstrates this question?
Given this input file:
$ identify -verbose input.tif
Image:
Filename: input.tif
Format: TIFF (Tagged Image File Format)
Mime type: image/tiff
Class: DirectClass
Geometry: 2998x4454+0+0
Resolution: 3000x3000
Print size: 0.999333x1.48467
Units: PixelsPerInch
I run the following:
sharp('input.tif').withMetadata({ density: 96 }).jpeg().toFile('output.jpg');
sharp('input.tif').withMetadata({ density: 96 }).png().toFile('output.png');
sharp('input.tif').withMetadata({ density: 96 }).tiff().toFile('output.tif');
The output looks like this:
$ identify -verbose output.jpg
Image:
Filename: output.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Mime type: image/jpeg
Class: DirectClass
Geometry: 2998x4454+0+0
Resolution: 96x96
Print size: 31.2292x46.3958
Units: PixelsPerInch
$ identify -verbose output.png
Image:
Filename: output.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 2998x4454+0+0
Resolution: 37.8x37.8
Print size: 79.3122x117.831
Units: PixelsPerCentimeter
$ identify -verbose output.tif
Image:
Filename: output.tif
Format: TIFF (Tagged Image File Format)
Mime type: image/tiff
Class: DirectClass
Geometry: 2998x4454+0+0
Resolution: 25.4x25.4
Print size: 118.031x175.354
Units: PixelsPerInch
I get why the JPEG and the PNG are using different units (because the PNG header always expresses density in pixels per meter), but at least the density math works out to 96 PPI. The TIFF keeps the original units, but gets written out using sharp's default density of 1000 pixels per meter.
FWIW, sharp is capable of reading the density from the source TIFF:
> await sharp('input.tif').metadata();
{
format: 'tiff',
width: 2998,
height: 4454,
space: 'b-w',
channels: 1,
depth: 'uchar',
density: 3000,
isProgressive: false,
pages: 1,
hasProfile: true,
hasAlpha: false,
orientation: 1,
...
}
Are you able to provide a sample image that helps explain the question?
Yes. (It's zipped just to prevent GitHub from trying to create a derivative or inlining it into the issue.)
input.tif.zip