fix(dicom-image-loader): use Float32Array for non-integer rescale slopes to prevent pixel data corruption#2707
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…pes to prevent pixel data corruption DICOM images with non-integer RescaleSlope (e.g. DTI FA maps with RescaleSlope=0.001) have their pixel data destroyed during preScale because getPixelDataTypeFromMinMax incorrectly selects Uint8Array. This happens because Number.isInteger(1.0) === true in JavaScript, so scaled min/max of 0.0 and 1.0 are treated as integers, leading to Uint8Array selection. All fractional values (0.013, 0.5, 0.999) are then truncated to 0. Fix: 1. In _handlePreScaleSetup: detect non-integer scaling parameters and force Float32Array before scaling is applied. 2. In setPixelDataType: skip re-typing if pixelData is already Float32Array, preventing the main thread from downgrading it back to Uint8Array after web worker transfer. Fixes: cornerstonejs#2706 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
… division by zero The DICOM LINEAR VOI formula uses (WW-1) which becomes 0 when WW=1, producing lower === upper (degenerate range). This causes division by zero in the VOI LUT shader, resulting in a binary black/white image. Fall back to LINEAR_EXACT (lower = WC - WW/2, upper = WC + WW/2) which correctly handles WW=1 (e.g. DTI FA with WC=0.5, WW=1 gives lower=0, upper=1). Fixes: cornerstonejs#2706 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Context
Fixes #2706
DICOM images with non-integer
RescaleSlope(e.g. DTI FA maps withRescaleSlope=0.001) render as completely black in StackViewport. These images display correctly in other viewers such as RadiAnt and OsiriX.The legacy Cornerstone had a similar issue (cornerstonejs/cornerstone#302, fixed in PR #303).
Two independent bugs are involved:
getPixelDataTypeFromMinMax(0.0, 1.0)selectsUint8ArraybecauseNumber.isInteger(1.0) === truein JavaScript. All fractional scaled values (0.013, 0.5, 0.999) are truncated to 0. This function is called twice (web worker + main threadsetPixelDataType), destroying the data at both stages.toLowHighRangewithWindowWidth=1produceslower === upper === 0via the LINEAR formula(WW-1) = 0, causing division by zero in the VOI shader and a binary black/white image.Changes & Results
_handlePreScaleSetupindecodeImageFrameWorker.js: Detect non-integer scaling parameters and forceFloat32ArraybeforegetPixelDataTypeFromMinMaxis called.setPixelDataTypeinsetPixelDataType.ts: Skip re-typing ifpixelDatais alreadyFloat32Array, preventing the main thread from downgrading it toUint8Array.toLowHighRangeinwindowLevel.ts: WhenWindowWidth <= 1with LINEAR function, fall back to LINEAR_EXACT (lower = WC - WW/2,upper = WC + WW/2) to produce a valid range.All three fixes are needed — removing any one results in either a black screen or a binary black/white image.
Testing
RescaleSlope=0.001in StackViewport — should display grayscale instead of blackRescaleSlope=1) — should be unaffectedWindowWidth > 1—toLowHighRangeshould use existing LINEAR formula unchangedChecklist
PR
semantic-release format and guidelines.
Code
etc.)
Public Documentation Updates
additions or removals.
Tested Environment
I may be wrong about some of the details — please correct me if I've misunderstood anything. Any feedback would be greatly appreciated. Thank you!