Comments (7)
https://sharp.pixelplumbing.com/api-output#png
[options.quality]
use the lowest number of colours needed to achieve given quality, setspalette
totrue
[options.palette]
quantise to a palette-based image with alpha transparency support
When quality
is set, palette
is also selected and therefore you have chosen to use a lossy, quantised output.
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Ah, I see. I understand that it's a lossy output, but the output from my example is still very unexpected for me. The background color is a single color, and it just adds a completely different color but just in some areas. Is this the desired/expected functionality?
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Is there any way to prevent this from happening while still setting a quality
?
from sharp.
The prebuilt binaries provided by sharp include the BSD-licenced libimagequant v2.4.1 for generating and mapping image palettes.
You may have some luck building your own libvips from source compiled with support for an alternative quantisation library such as a more recent GPL-licenced libimagequant or quantizr, but this is left as an exercise for the reader.
from sharp.
Thanks! I ended up setting dither
to 0.0
, which seems to fix the issue in all instances I tested. To your knowledge, should this reliably fix the issue?
from sharp.
Ah yes, this does look like dithering gone a bit wrong, so altering the dither
level until you find a value that works for the type of input you'll be processing is definitely a good idea.
from sharp.
I hope this information helped. Please feel free to re-open with more details if further assistance is required.
from sharp.
Related Issues (20)
- if the image is a QR code or contains a QR code, the result is larger than the original image. HOT 4
- `tocolorspace` and `png({quality:x})` are mutually exclusive. HOT 2
- Error sharp with HEIC files - bad seek to 293616\nheif: Unsupported feature: Unsupported codec (4.3000) HOT 3
- Webpack node-loader support + cross-compilation HOT 4
- Handling HEIC files in an Electron application and distributing HOT 2
- Unexpected rotation behavior for different size outputs after upgrading Sharp HOT 1
- Feature Request: Please support running in a browser (without node.js) HOT 2
- electon,win32,ia32,install ok,but pack and run ,it's error,"The specified procedure could not be found." HOT 3
- how to cache sharp binaries? HOT 1
- Sharp HEIC export is 4.4x bigger than equivalent macOS Finder export HOT 5
- Vercel production issue: .jpeg({ quality: XX }) not working at all - works in local env HOT 9
- PNG Conversion Failure HOT 2
- Resizing results in low quality/blurry image HOT 6
- Resize images while keeping the ICC profile and color space HOT 4
- Installation fails when trying to install as a dependency with global libvips on macOS HOT 4
- sharp 在获取某些webp图片元数据时导致文件句柄未被正确释放 HOT 2
- Sharp is present in node_modules but still got error in server logs. Error: 'sharp' is required to be installed in standalone mode. HOT 8
- Bug: type metadata.chromaSubsampling as union with undefined HOT 1
- Channel excluded from image manipulations, if the channel was `join`ed at later time HOT 4
- In network contrained environement we shoud have a diferent url for github like an artifactory proxy HOT 1
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