FA-70302 / Map projection transforms / Member archive

World file to corner geotransform and pixel centre: pixel centre origin · case 02

Pixel-centre eastings are half a pixel west of where the world file puts them.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input [lines, col, row] where lines are the six world-file values in file order A, D, B, E, C, F: A and E are the pixel sizes, D and B the rotation terms, and (C, F) the map coordinate of the centre of the upper-left pixel. Return the corner-based geotransform [C - A/2 - B/2, A, B, F - D/2 - E/2, D, E] followed by the centre of pixel (col, row): C + A*col + B*row and F + D*col + E*row; all rounded to 6 decimals.

Why this case matters

GIS tools interchange world files and corner-origin geotransforms; the half-pixel convention and line order are classic sources of half-pixel and rotated-raster shifts.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
control #1	`[-180.0, 0.25, 0.0, 90.0, 0.0, -0.25, -167.5, 81.125]`	`[-180.0, 0.25, 0.0, 90.0, 0.0, -0.25, -167.375, 81.125]`	Failed

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