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Drawing a page: name the decoders, as render's README does #19

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tannevaled merged 1 commit into from
Oct 18, 2026
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Drawing a page: name the decoders, as render's README does #19

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15 changes: 13 additions & 2 deletions content/working-with-a-file/rendering.md
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Expand Up @@ -27,8 +27,19 @@ XObjects with their own matrix, box and resources.

Images at every bit depth and colour space, with a `/Decode` array, as
one-bit stencils painted in the colour in force, and with either kind of
transparency. A JPEG is decoded by the standard library; a format nothing
here reads is left undrawn rather than drawn wrong.
transparency. A format nothing here reads is left undrawn rather than drawn
wrong. Which decoder runs is part of what is drawn, so it is named:

| filter | decoder |
|---|---|
| `/DCTDecode` | [`go-images/jpeg`](https://github.com/go-images/jpeg), Go's own `image/jpeg` with one change: a four-component picture's chroma is upsampled the way libjpeg does, not by repeating each sample |
| `/JPXDecode` | [`go-images/jpeg2000`](https://github.com/go-images/jpeg2000), a fork that reads a CMYK file as ink, and decodes a lossless picture 2.4× faster on amd64 than it did before v0.13.7 |
| `/JBIG2Decode` | `go-gfx/gfx/codec`, where the fleet keeps its image decoders |
| `/CCITTFaxDecode`, `/FlateDecode`, `/LZWDecode`, `/RunLengthDecode` | `go-pdfkit/reader`, which runs them to samples |

This page used to say that a JPEG is decoded by the standard library. That
stopped being true when the `jpeg` fork was taken, and render's README had
already been corrected.

Text from an embedded **TrueType**, **OpenType**, **bare CFF** or
**PostScript Type 1** program, from a composite font addressed by character
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