Speed up `Image.getchannel()`, `Image.merge()`, `Image.putalpha()` and `Image.split()` by akx · Pull Request #9675 · python-pillow/Pillow

akx · 2026-06-16T12:56:12Z

Refs #9649 (same technique, different loops).

On my machine, this speeds up .merge() for RGB images by about 3x according to the benchmark code from #9654.

radarhere · 2026-06-16T13:26:57Z

@@ -47,16 +47,19 @@ ImagingGetBand(Imaging imIn, int band) {
    }

    /* Extract band from image */


Suggested change

/* Extract band from image */

// Extract band from image

Maybe this is nicer than having a multiline comment next to a single line comment?

Not sure it matters that much? I just didn't want to touch the original code or comment format here :)

radarhere · 2026-06-16T13:27:08Z

@@ -92,33 +95,37 @@ ImagingSplit(Imaging imIn, Imaging bands[4]) {
    }

    /* Extract bands from image */


Suggested change

/* Extract bands from image */

// Extract bands from image

radarhere · 2026-06-16T13:27:18Z

@@ -195,10 +202,13 @@ ImagingPutBand(Imaging imOut, Imaging imIn, int band) {
    }

    /* Insert band into image */


Suggested change

/* Insert band into image */

// Insert band into image

hugovk · 2026-06-29T15:27:10Z

Updated now #9654 is merged.

codspeed-hq · 2026-06-29T15:44:37Z

Merging this PR will improve performance by 85.18%

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 3 improved benchmarks
✅ 328 untouched benchmarks

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	`test_merge[1024x1024-RGBA]`	10.1 ms	5.4 ms	+87.77%
⚡	`test_merge[1024x1024-RGB]`	8.4 ms	4.5 ms	+86.05%
⚡	`test_merge[1024x1024-LA]`	6.7 ms	3.7 ms	+81.78%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing akx:bands-loops (23f5f76) with main (086fa4a)}

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [pillow](https://github.com/python-pillow/Pillow) ([changelog](https://github.com/python-pillow/Pillow/releases)) | `<12.2.1,>=12.2.0` → `<12.3.1,>=12.3.0` | ![age](https://developer.mend.io/api/mc/badges/age/pypi/pillow/12.3.0?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/pillow/12.2.0/12.3.0?slim=true) | --- ### Release Notes <details> <summary>python-pillow/Pillow (pillow)</summary> ### [`v12.3.0`](https://github.com/python-pillow/Pillow/releases/tag/12.3.0) [Compare Source](python-pillow/Pillow@12.2.0...12.3.0) <https://pillow.readthedocs.io/en/stable/releasenotes/12.3.0.html> #### Removals - Remove non-image ImageCms modes [#9697](python-pillow/Pillow#9697) \[[@radarhere](https://github.com/radarhere)] #### Documentation - Add release notes for SBOM and performance improvements [#9747](python-pillow/Pillow#9747) \[[@radarhere](https://github.com/radarhere)] - Add security release notes [#9741](python-pillow/Pillow#9741) \[[@radarhere](https://github.com/radarhere)] - Add release notes for Python 3.15 beta wheels [#9696](python-pillow/Pillow#9696) \[[@radarhere](https://github.com/radarhere)] - ImageFont can also be used with ImageText [#9597](python-pillow/Pillow#9597) \[[@radarhere](https://github.com/radarhere)] - Additional guidelines for security reports [#9659](python-pillow/Pillow#9659) \[[@wiredfool](https://github.com/wiredfool)] - Fixed typo [#9636](python-pillow/Pillow#9636) \[[@radarhere](https://github.com/radarhere)] - Added CVEs to 12.2.0 release notes [#9591](python-pillow/Pillow#9591) \[[@radarhere](https://github.com/radarhere)] - Revise development support information in README [#9583](python-pillow/Pillow#9583) \[[@aclark4life](https://github.com/aclark4life)] - Add INCIDENT\_RESPONSE.md [#9555](python-pillow/Pillow#9555) \[[@aclark4life](https://github.com/aclark4life)] - Add STRIDE threat model to security docs [#9562](python-pillow/Pillow#9562) \[[@aclark4life](https://github.com/aclark4life)] - Add CVEs to 12.2.0 release notes [#9556](python-pillow/Pillow#9556) \[[@radarhere](https://github.com/radarhere)] - Update README with revised security policy [#9553](python-pillow/Pillow#9553) \[[@radarhere](https://github.com/radarhere)] - Update security policy [#9552](python-pillow/Pillow#9552) \[[@aclark4life](https://github.com/aclark4life)] - Update macOS tested Python versions [#9534](python-pillow/Pillow#9534) \[[@radarhere](https://github.com/radarhere)] #### Dependencies - Update dependency harfbuzz to v14.2.1 [#9720](python-pillow/Pillow#9720) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency mypy to v2 [#9653](python-pillow/Pillow#9653) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency cibuildwheel to v4 [#9665](python-pillow/Pillow#9665) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update github-actions [#9655](python-pillow/Pillow#9655) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency libavif to v1.4.2 [#9652](python-pillow/Pillow#9652) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency lcms2 to v2.19.1 [#9651](python-pillow/Pillow#9651) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency check-jsonschema to v0.37.2 [#9650](python-pillow/Pillow#9650) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update google/oss-fuzz digest to [`d872252`](python-pillow/Pillow@d872252) [#9614](python-pillow/Pillow#9614) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency lcms2 to v2.19 [#9609](python-pillow/Pillow#9609) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency libpng to v1.6.58 - autoclosed [#9608](python-pillow/Pillow#9608) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency harfbuzz to v14 [#9610](python-pillow/Pillow#9610) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency mypy to v1.20.2 [#9599](python-pillow/Pillow#9599) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update github-actions [#9611](python-pillow/Pillow#9611) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update dependency cibuildwheel to v3.4.1 [#9607](python-pillow/Pillow#9607) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Move dependency versions to single JSON and enable Renovate [#9559](python-pillow/Pillow#9559) \[[@hugovk](https://github.com/hugovk)] - Updated raqm to 0.10.5 [#9557](python-pillow/Pillow#9557) \[[@radarhere](https://github.com/radarhere)] - Update dependency cibuildwheel to v3.4.0 [#9532](python-pillow/Pillow#9532) \[@[renovate\[bot\]](https://github.com/apps/renovate)] #### Testing - Remove matrix.os from benchmark [#9735](python-pillow/Pillow#9735) \[[@radarhere](https://github.com/radarhere)] - Remove references to libavif patch [#9734](python-pillow/Pillow#9734) \[[@radarhere](https://github.com/radarhere)] - Add benchmark tests [#9654](python-pillow/Pillow#9654) \[[@akx](https://github.com/akx)] - Use reshape() instead of setting NumPy array shape directly [#9728](python-pillow/Pillow#9728) \[[@radarhere](https://github.com/radarhere)] - Add dependencies.json to Windows cache key [#9721](python-pillow/Pillow#9721) \[[@radarhere](https://github.com/radarhere)] - Increase AVIF test epsilon for loong64 [#9714](python-pillow/Pillow#9714) \[[@wszqkzqk](https://github.com/wszqkzqk)] - Add colour to Linux and Windows wheel build logs [#9677](python-pillow/Pillow#9677) \[[@hugovk](https://github.com/hugovk)] - Do not test NumPy against Python 3.15 Windows AMD64 wheels [#9674](python-pillow/Pillow#9674) \[[@radarhere](https://github.com/radarhere)] - Run pyroma in `tox -e lint` instead of pytest [#9670](python-pillow/Pillow#9670) \[[@hugovk](https://github.com/hugovk)] - Update Ghostscript to 10.7.1 [#9634](python-pillow/Pillow#9634) \[[@radarhere](https://github.com/radarhere)] - Update free-threading CI [#9625](python-pillow/Pillow#9625) \[[@hugovk](https://github.com/hugovk)] - Increase AVIF test epsilon for riscv64 [#9606](python-pillow/Pillow#9606) \[[@radarhere](https://github.com/radarhere)] - Add Fedora 44 [#9594](python-pillow/Pillow#9594) \[[@radarhere](https://github.com/radarhere)] - Test Ubuntu 26.04 LTS (Resolute Raccoon) [#9587](python-pillow/Pillow#9587) \[[@hugovk](https://github.com/hugovk)] - Skip EPS test\_1 for Ghostscript 10.06.0 [#9588](python-pillow/Pillow#9588) \[[@radarhere](https://github.com/radarhere)] - Catch subprocess.CalledProcessError in test\_grab\_x11 [#9578](python-pillow/Pillow#9578) \[[@radarhere](https://github.com/radarhere)] - Correct feature name [#9542](python-pillow/Pillow#9542) \[[@radarhere](https://github.com/radarhere)] - Skip test if FreeType is not available [#9540](python-pillow/Pillow#9540) \[[@radarhere](https://github.com/radarhere)] - Remove type hint ignore [#9538](python-pillow/Pillow#9538) \[[@radarhere](https://github.com/radarhere)] - Update macOS tested Python versions [#9534](python-pillow/Pillow#9534) \[[@radarhere](https://github.com/radarhere)] - Remove Debian 12 and Fedora 42 from CI [#9530](python-pillow/Pillow#9530) \[[@hugovk](https://github.com/hugovk)] - Remove manylinux2014 and Amazon Linux 2 [#9528](python-pillow/Pillow#9528) \[[@radarhere](https://github.com/radarhere)] #### Type hints - Use NumPy 2.4.6 for mypy [#9705](python-pillow/Pillow#9705) \[[@radarhere](https://github.com/radarhere)] - Update dependency mypy to v2 [#9653](python-pillow/Pillow#9653) \[@[renovate\[bot\]](https://github.com/apps/renovate)] - Update putpixel type hint to allow lists in xy [#9585](python-pillow/Pillow#9585) \[[@radarhere](https://github.com/radarhere)] - Remove type hint ignore [#9538](python-pillow/Pillow#9538) \[[@radarhere](https://github.com/radarhere)] #### Other changes - Speed up ImageChops operations [#9738](python-pillow/Pillow#9738) \[[@akx](https://github.com/akx)] - Speed up `Image.filter()` [#9736](python-pillow/Pillow#9736) \[[@akx](https://github.com/akx)] - Speed up `Image.getchannel()`, `Image.merge()`, `Image.putalpha()` and `Image.split()` [#9675](python-pillow/Pillow#9675) \[[@akx](https://github.com/akx)] - Speed up `Image.fill()`, `Image.linear_gradient()` and `Image.radial_gradient()`. [#9737](python-pillow/Pillow#9737) \[[@akx](https://github.com/akx)] - Speed up `Image.resample()` [#9739](python-pillow/Pillow#9739) \[[@akx](https://github.com/akx)] - Speed up `alpha_composite`, `matrix`, `negative`, `quantize` [#9740](python-pillow/Pillow#9740) \[[@akx](https://github.com/akx)] - Remove PyErr\_Clear() of "weird" exceptions [#9730](python-pillow/Pillow#9730) \[[@radarhere](https://github.com/radarhere)] - Check realloc return value [#9722](python-pillow/Pillow#9722) \[[@radarhere](https://github.com/radarhere)] - Add max\_length to PdfStream decode() [#9718](python-pillow/Pillow#9718) \[[@radarhere](https://github.com/radarhere)] - Return early when there is no fill region [#9732](python-pillow/Pillow#9732) \[[@radarhere](https://github.com/radarhere)] - Allow error to be raised if PyDict\_SetItemString fails [#9731](python-pillow/Pillow#9731) \[[@radarhere](https://github.com/radarhere)] - Speed up `Image.blend()` [#9649](python-pillow/Pillow#9649) \[[@akx](https://github.com/akx)] - Raise OverflowError if number of vertices is too large for Path [#9729](python-pillow/Pillow#9729) \[[@radarhere](https://github.com/radarhere)] - Remove unused HSV and LAB matrix conversion from C [#9724](python-pillow/Pillow#9724) \[[@radarhere](https://github.com/radarhere)] - Prevent reusing ImagingDecoderObject.setimage [#9656](python-pillow/Pillow#9656) \[[@Serotav](https://github.com/Serotav)] - Raise ValueError if FPX tile size is not 64px by 64px [#9660](python-pillow/Pillow#9660) \[[@radarhere](https://github.com/radarhere)] - Only clear error if it is BufferError [#9727](python-pillow/Pillow#9727) \[[@radarhere](https://github.com/radarhere)] - Apply XOR mask to 1 and L mode CUR images [#9641](python-pillow/Pillow#9641) \[[@radarhere](https://github.com/radarhere)] - Do not raise error from unknown channel ID when parsing PSD layers [#9644](python-pillow/Pillow#9644) \[[@radarhere](https://github.com/radarhere)] - Raise ValueError if P;2L or P;4L data is truncated in frombytes() [#9725](python-pillow/Pillow#9725) \[[@radarhere](https://github.com/radarhere)] - Embed SBOM into wheels [#9679](python-pillow/Pillow#9679) \[[@hugovk](https://github.com/hugovk)] - Do not set eval() globals in ImageMath.unsafe\_eval() [#9576](python-pillow/Pillow#9576) \[[@radarhere](https://github.com/radarhere)] - Add Tcl/Tk license to wheels [#9663](python-pillow/Pillow#9663) \[[@radarhere](https://github.com/radarhere)] - Ensure map stride is at least one full row of pixels [#9719](python-pillow/Pillow#9719) \[[@radarhere](https://github.com/radarhere)] - Raise OverflowError if text width exceeds INT\_MAX [#9717](python-pillow/Pillow#9717) \[[@radarhere](https://github.com/radarhere)] - Raise error if image modes do not match ImageCms transform modes [#9715](python-pillow/Pillow#9715) \[[@radarhere](https://github.com/radarhere)] - Use int64\_t for text height [#9716](python-pillow/Pillow#9716) \[[@radarhere](https://github.com/radarhere)] - Return if error occurs in Py\_mod\_exec slot [#9712](python-pillow/Pillow#9712) \[[@radarhere](https://github.com/radarhere)] - Add decompression bomb checks to FontFile classes [#9711](python-pillow/Pillow#9711) \[[@radarhere](https://github.com/radarhere)] - If C error is raised, return NULL [#9706](python-pillow/Pillow#9706) \[[@radarhere](https://github.com/radarhere)] - Prevent saving 1 mode images as TGA with run-length encoding [#9709](python-pillow/Pillow#9709) \[[@radarhere](https://github.com/radarhere)] - Raise ValueError if EPS BeginBinary bytecount is negative [#9708](python-pillow/Pillow#9708) \[[@radarhere](https://github.com/radarhere)] - Do not DECREF tuple until tuple items are no longer used [#9707](python-pillow/Pillow#9707) \[[@radarhere](https://github.com/radarhere)] - Do not update NumPy automatically [#9713](python-pillow/Pillow#9713) \[[@radarhere](https://github.com/radarhere)] - Simplified code [#9642](python-pillow/Pillow#9642) \[[@radarhere](https://github.com/radarhere)] - If realloc fails, do not reduce block size [#9702](python-pillow/Pillow#9702) \[[@radarhere](https://github.com/radarhere)] - DECREF PyDict\_GetItemRef result [#9701](python-pillow/Pillow#9701) \[[@radarhere](https://github.com/radarhere)] - Use int64\_t to calculate paste box dimensions [#9703](python-pillow/Pillow#9703) \[[@radarhere](https://github.com/radarhere)] - Calculate JPEG2000 total\_component\_width for each tile in isolation [#9704](python-pillow/Pillow#9704) \[[@radarhere](https://github.com/radarhere)] - Raise ValueError if value is not bytes for TIFF\_BYTE or TIFF\_ASCII tag [#9699](python-pillow/Pillow#9699) \[[@radarhere](https://github.com/radarhere)] - Release Py\_Buffer on error [#9698](python-pillow/Pillow#9698) \[[@radarhere](https://github.com/radarhere)] - Use os.startfile() in WindowsViewer show\_file() [#9692](python-pillow/Pillow#9692) \[[@radarhere](https://github.com/radarhere)] - Validate large filter sizes when initializing RankFilter [#9695](python-pillow/Pillow#9695) \[[@radarhere](https://github.com/radarhere)] - Add decompression bomb check to GdImageFile [#9693](python-pillow/Pillow#9693) \[[@radarhere](https://github.com/radarhere)] - Free image bands when an error occurs while splitting an image [#9694](python-pillow/Pillow#9694) \[[@radarhere](https://github.com/radarhere)] - Check PyList\_Append return value [#9690](python-pillow/Pillow#9690) \[[@radarhere](https://github.com/radarhere)] - Check WebPMuxNew return value [#9689](python-pillow/Pillow#9689) \[[@radarhere](https://github.com/radarhere)] - Check PyCapsule\_New return value [#9691](python-pillow/Pillow#9691) \[[@radarhere](https://github.com/radarhere)] - Do not return negative width for text length [#9623](python-pillow/Pillow#9623) \[[@radarhere](https://github.com/radarhere)] - Add args argument to METH\_NOARGS methods [#9687](python-pillow/Pillow#9687) \[[@radarhere](https://github.com/radarhere)] - Check ImagingNewDirty return value [#9688](python-pillow/Pillow#9688) \[[@radarhere](https://github.com/radarhere)] - Use int64\_t for text width [#9686](python-pillow/Pillow#9686) \[[@radarhere](https://github.com/radarhere)] - Move PyDateTime\_IMPORT inside Py\_mod\_exec slot [#9580](python-pillow/Pillow#9580) \[[@radarhere](https://github.com/radarhere)] - Validate size and rank when initializing RankFilter [#9661](python-pillow/Pillow#9661) \[[@radarhere](https://github.com/radarhere)] - Raise ValueError if insufficient data is read from DDS RGB file [#9405](python-pillow/Pillow#9405) \[[@radarhere](https://github.com/radarhere)] - Correct `IFDRational.__float__()` return value [#9676](python-pillow/Pillow#9676) \[[@nyxst4ck](https://github.com/nyxst4ck)] - Correct length when accessing ImagePath.Path subscript [#9685](python-pillow/Pillow#9685) \[[@radarhere](https://github.com/radarhere)] - Release reference on non-flattened sequence error [#9684](python-pillow/Pillow#9684) \[[@radarhere](https://github.com/radarhere)] - Do not release Py\_buffer until buf is no longer in use [#9683](python-pillow/Pillow#9683) \[[@radarhere](https://github.com/radarhere)] - Do not resize macOS retina screenshots by default [#9266](python-pillow/Pillow#9266) \[[@radarhere](https://github.com/radarhere)] - Add abstract BaseImageFont class [#9595](python-pillow/Pillow#9595) \[[@radarhere](https://github.com/radarhere)] - Cast before multiplying [#9678](python-pillow/Pillow#9678) \[[@radarhere](https://github.com/radarhere)] - Limit radius to half width or height of rounded rectangle [#9561](python-pillow/Pillow#9561) \[[@radarhere](https://github.com/radarhere)] - linesize is always xsize multiplied by pixelsize [#9647](python-pillow/Pillow#9647) \[[@radarhere](https://github.com/radarhere)] - Check annotate\_hash\_table return value [#9572](python-pillow/Pillow#9572) \[[@radarhere](https://github.com/radarhere)] - Catch KeyError when checking mode from PNG IHDR chunk [#9604](python-pillow/Pillow#9604) \[[@radarhere](https://github.com/radarhere)] - Only pass one argument to C expand [#9664](python-pillow/Pillow#9664) \[[@radarhere](https://github.com/radarhere)] - Raise error if declared JPEG2000 marker length is too small [#9666](python-pillow/Pillow#9666) \[[@radarhere](https://github.com/radarhere)] - In \_dump(), use Python PPM save, instead of C [#9566](python-pillow/Pillow#9566) \[[@radarhere](https://github.com/radarhere)] - Raise error consistently from inside ImagingNewArrow [#9571](python-pillow/Pillow#9571) \[[@radarhere](https://github.com/radarhere)] - Simplify `RankFilter.c` check [#9662](python-pillow/Pillow#9662) \[[@radarhere](https://github.com/radarhere)] - Support opening and saving L mode AVIF images with libavif >= 1.3.0 [#9471](python-pillow/Pillow#9471) \[[@radarhere](https://github.com/radarhere)] - \[pre-commit.ci] pre-commit autoupdate [#9648](python-pillow/Pillow#9648) \[@[pre-commit-ci\[bot\]](https://github.com/apps/pre-commit-ci)] - Apply libtiff patch to fix CVE-2026-4775 [#9646](python-pillow/Pillow#9646) \[[@radarhere](https://github.com/radarhere)] - Remove duplicate code [#9640](python-pillow/Pillow#9640) \[[@radarhere](https://github.com/radarhere)] - Switch iOS back to macos-26-intel [#9631](python-pillow/Pillow#9631) \[[@radarhere](https://github.com/radarhere)] - Don't use list as default in PdfParser read\_prev\_trailer [#9629](python-pillow/Pillow#9629) \[[@danigm](https://github.com/danigm)] - Add support for Python 3.15 [#9624](python-pillow/Pillow#9624) \[[@radarhere](https://github.com/radarhere)] - Do not draw line or arc if width is zero [#9589](python-pillow/Pillow#9589) \[[@radarhere](https://github.com/radarhere)] - Use \_accept check in WebP \_open [#9605](python-pillow/Pillow#9605) \[[@radarhere](https://github.com/radarhere)] - Compare dist sizes vs latest PyPI release [#9621](python-pillow/Pillow#9621) \[[@hugovk](https://github.com/hugovk)] - Do not generate SBOM in scheduled run on fork [#9620](python-pillow/Pillow#9620) \[[@radarhere](https://github.com/radarhere)] - Use plugin method directly when saving PDFs [#9547](python-pillow/Pillow#9547) \[[@radarhere](https://github.com/radarhere)] - \[pre-commit.ci] pre-commit autoupdate [#9617](python-pillow/Pillow#9617) \[@[pre-commit-ci\[bot\]](https://github.com/apps/pre-commit-ci)] - Set Renovate prCreation to not-pending [#9616](python-pillow/Pillow#9616) \[[@radarhere](https://github.com/radarhere)] - Raise error if PNG transparency has incorrect type or length when saving [#9536](python-pillow/Pillow#9536) \[[@radarhere](https://github.com/radarhere)] - If PdfParser buffer is memoryview, release it when closing [#9596](python-pillow/Pillow#9596) \[[@radarhere](https://github.com/radarhere)] - Correct integer overflow in 16-bit resampling [#9480](python-pillow/Pillow#9480) \[[@hayatoikoma](https://github.com/hayatoikoma)] - SBOM: Use real versions from dependencies.json [#9593](python-pillow/Pillow#9593) \[[@hugovk](https://github.com/hugovk)] - Restrict SBOM upload to only Pillow JSON [#9598](python-pillow/Pillow#9598) \[[@radarhere](https://github.com/radarhere)] - Generate CycloneDX SBOM at release time via CI [#9550](python-pillow/Pillow#9550) \[[@aclark4life](https://github.com/aclark4life)] - Raise ValueError if ImageOps border has unsupported format [#9426](python-pillow/Pillow#9426) \[[@veeceey](https://github.com/veeceey)] - Unsafe pointer dereference from unchecked Python integer in Tk initialization [#9548](python-pillow/Pillow#9548) \[[@barttran2k](https://github.com/barttran2k)] - Reorder renovate.json [#9565](python-pillow/Pillow#9565) \[[@radarhere](https://github.com/radarhere)] - Add python-pillow GitHub Sponsors to FUNDING.yml [#9563](python-pillow/Pillow#9563) \[[@aclark4life](https://github.com/aclark4life)] - Correct environment URL [#9558](python-pillow/Pillow#9558) \[[@radarhere](https://github.com/radarhere)] - Remove or protect secrets in Actions [#9544](python-pillow/Pillow#9544) \[@[pre-commit-ci\[bot\]](https://github.com/apps/pre-commit-ci)] - Move Homebrew dependencies into Brewfile [#9546](python-pillow/Pillow#9546) \[[@hugovk](https://github.com/hugovk)] - Do not precompute horizontal coefficients if not horizontal resizing [#9543](python-pillow/Pillow#9543) \[[@radarhere](https://github.com/radarhere)] - Fix comparison warnings [#9541](python-pillow/Pillow#9541) \[[@radarhere](https://github.com/radarhere)] - Close PdfParser if error occurs during init [#9539](python-pillow/Pillow#9539) \[[@radarhere](https://github.com/radarhere)] - Drop experimental Python 3.13 free-threaded wheels [#9535](python-pillow/Pillow#9535) \[[@radarhere](https://github.com/radarhere)] - Update github-actions [#9533](python-pillow/Pillow#9533) \[@[renovate\[bot\]](https://github.com/apps/renovate)] </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR is behind base branch, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.tainton.uk/repos/webexmemebot/pulls/596 Co-authored-by: renovate[bot] <renovate-bot@git.tainton.uk> Co-committed-by: renovate[bot] <renovate-bot@git.tainton.uk>

radarhere added the Performance label Jun 16, 2026

radarhere changed the title ~~Speed up .merge()/.split() and friends~~ Speed up Image.getchannel(), Image.merge(), Image.putalpha() and Image.split() Jun 16, 2026

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hugovk force-pushed the bands-loops branch from ee7d44c to 4129822 Compare June 29, 2026 15:27

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Comment thread src/libImaging/Bands.c Outdated

Bands: hoist size vars and add restrict in split/merge/getband/putband

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akx force-pushed the bands-loops branch from 4129822 to 23f5f76 Compare June 29, 2026 20:25

radarhere mentioned this pull request Jun 30, 2026

Add release notes for SBOM and performance improvements #9747

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hugovk merged commit a94578c into python-pillow:main Jul 1, 2026
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Document the internal image distinctness constraints #9752

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Speed up Image.offset #9753

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Speed up `Image.getchannel()`, `Image.merge()`, `Image.putalpha()` and `Image.split()`#9675

Speed up `Image.getchannel()`, `Image.merge()`, `Image.putalpha()` and `Image.split()`#9675
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akx:bands-loops

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		@@ -47,16 +47,19 @@ ImagingGetBand(Imaging imIn, int band) {
		}

		/* Extract band from image */

		@@ -92,33 +95,37 @@ ImagingSplit(Imaging imIn, Imaging bands[4]) {
		}

		/* Extract bands from image */

		@@ -195,10 +202,13 @@ ImagingPutBand(Imaging imOut, Imaging imIn, int band) {
		}

		/* Insert band into image */

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Merging this PR will improve performance by 85.18%

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