summaryrefslogtreecommitdiff
path: root/gerbonara/gerber/tests/test_rs274x.py
blob: 13192a339be3e8aba6d4c53c2db18c5052cbb581 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
#! /usr/bin/env python
# -*- coding: utf-8 -*-
# Author: Jan Götte <code@jaseg.de>
import math

from PIL import Image
import pytest

from ..rs274x import GerberFile
from ..cam import FileSettings

from .image_support import *
from .utils import *

REFERENCE_FILES = [ l.strip() for l in '''
    board_outline.GKO
    example_outline_with_arcs.gbr
    example_two_square_boxes.gbr
    example_coincident_hole.gbr
    example_cutin.gbr
    example_cutin_multiple.gbr
    example_flash_circle.gbr
    example_flash_obround.gbr
    example_flash_polygon.gbr
    example_flash_rectangle.gbr
    example_fully_coincident.gbr
    example_guess_by_content.g0
    example_holes_dont_clear.gbr
    example_level_holes.gbr
    example_not_overlapping_contour.gbr
    example_not_overlapping_touching.gbr
    example_overlapping_contour.gbr
    example_overlapping_touching.gbr
    example_simple_contour.gbr
    example_single_contour_1.gbr
    example_single_contour_2.gbr
    example_single_contour_3.gbr
    example_am_exposure_modifier.gbr
    bottom_copper.GBL
    bottom_mask.GBS
    bottom_silk.GBO
    eagle_files/copper_bottom_l4.gbr
    eagle_files/copper_inner_l2.gbr
    eagle_files/copper_inner_l3.gbr
    eagle_files/copper_top_l1.gbr
    eagle_files/profile.gbr
    eagle_files/silkscreen_bottom.gbr
    eagle_files/silkscreen_top.gbr
    eagle_files/soldermask_bottom.gbr
    eagle_files/soldermask_top.gbr
    eagle_files/solderpaste_bottom.gbr
    eagle_files/solderpaste_top.gbr
    multiline_read.ger
    test_fine_lines_x.gbr
    test_fine_lines_y.gbr
    top_copper.GTL
    top_mask.GTS
    top_silk.GTO
    open_outline_altium.gbr
    easyeda/Gerber_TopSolderMaskLayer.GTS
    easyeda/Gerber_TopSilkLayer.GTO
    easyeda/Gerber_BottomSolderMaskLayer.GBS
    easyeda/Gerber_BoardOutline.GKO
    easyeda/Gerber_TopLayer.GTL
    easyeda/Gerber_BottomLayer.GBL
    easyeda/Gerber_TopPasteMaskLayer.GTP
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr2.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr3.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_fab.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr10_GAF.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr7.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_sps.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr6.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr1_GAF.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_assy.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_smc_GAF.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr4.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr5.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_bslk.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_spc.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_tslk_GAF.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr8.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_sms_GAF.art
    allegro-2/MinnowMax_RevA1_GAF_Gerber/MinnowMax_lyr9.art
    eagle-newer/solderpaste_bottom.gbr
    eagle-newer/silkscreen_bottom.gbr
    eagle-newer/profile.gbr
    eagle-newer/copper_bottom.gbr
    eagle-newer/soldermask_top.gbr
    eagle-newer/solderpaste_top.gbr
    eagle-newer/soldermask_bottom.gbr
    eagle-newer/silkscreen_top.gbr
    eagle-newer/copper_top.gbr
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G4
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G9
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GBL
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GTO
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G11
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G1
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GBP
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G2
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GM15
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GTS
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G6
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G7
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G3
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GPB
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GM1
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G12
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GBS
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GTL
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G10
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GM14
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G5
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GTP
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GBO
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.G8
    altium-composite-drill/Gerber/LimeSDR-QPCIe_1v2.GPT
    geda/driver.topmask.gbr
    geda/controller.top.gbr
    geda/controller.bottom.gbr
    geda/driver.bottommask.gbr
    geda/driver.top.gbr
    geda/driver.bottom.gbr
    geda/controller.topsilk.gbr
    geda/controller.fab.gbr
    geda/driver.topsilk.gbr
    geda/controller.group3.gbr
    geda/controller.topmask.gbr
    geda/driver.group5.gbr
    geda/controller.bottommask.gbr
    geda/driver.fab.gbr
    pcb-rnd/power-art.gko
    pcb-rnd/power-art.ast
    pcb-rnd/power-art.gtl
    pcb-rnd/power-art.lht
    pcb-rnd/power-art.gto
    pcb-rnd/power-art.gtp
    pcb-rnd/power-art.asb
    pcb-rnd/power-art.gbp
    pcb-rnd/power-art.gbs
    pcb-rnd/power-art.gbl
    pcb-rnd/power-art.fab
    pcb-rnd/power-art.gbo
    pcb-rnd/power-art.gts
    siemens/80101_0125_F200_L04.gdo
    siemens/80101_0125_F200_L12_Bottom.gdo
    siemens/80101_0125_F200_L11.gdo
    siemens/80101_0125_F200_L10.gdo
    siemens/80101_0125_F200_SolderPasteTop.gdo
    siemens/80101_0125_F200_SoldermaskTop.gdo
    siemens/80101_0125_F200_L06.gdo
    siemens/80101_0125_F200_L02.gdo
    siemens/80101_0125_F200_SilkscreenBottom.gdo
    siemens/80101_0125_F200_SoldermaskBottom.gdo
    siemens/80101_0125_F200_SolderPasteBottom.gdo
    siemens/80101_0125_F200_L03.gdo
    siemens/80101_0125_F200_L01_Top.gdo
    Target3001/IRNASIoTbank1.2.Bot
    Target3001/IRNASIoTbank1.2.Outline
    Target3001/IRNASIoTbank1.2.PasteBot
    Target3001/IRNASIoTbank1.2.PasteTop
    Target3001/IRNASIoTbank1.2.PosiBot
    Target3001/IRNASIoTbank1.2.PosiTop
    Target3001/IRNASIoTbank1.2.StopBot
    Target3001/IRNASIoTbank1.2.StopTop
    Target3001/IRNASIoTbank1.2.Top
    kicad-older/chibi_2024-Edge.Cuts.gbr
    kicad-older/chibi_2024-F.SilkS.gbr
    kicad-older/chibi_2024-B.Paste.gbr
    kicad-older/chibi_2024-B.Cu.gbr
    kicad-older/chibi_2024-F.Mask.gbr
    kicad-older/chibi_2024-B.Mask.gbr
    kicad-older/chibi_2024-F.Paste.gbr
    kicad-older/chibi_2024-B.SilkS.gbr
    kicad-older/chibi_2024-F.Cu.gbr
    fritzing/combined.gbs
    fritzing/combined.gm1
    fritzing/combined.gbl
    fritzing/combined.gbo
    fritzing/combined.GKO
    fritzing/combined.gtl
    fritzing/combined.gts
    fritzing/combined.gto
    siemens-2/Gerber/SoldermaskTop.gdo
    siemens-2/Gerber/EtchLayerTop.gdo
    siemens-2/Gerber/DrillDrawingThrough.gdo
    siemens-2/Gerber/SoldermaskBottom.gdo
    siemens-2/Gerber/SolderPasteBottom.gdo
    siemens-2/Gerber/SolderPasteTop.gdo
    siemens-2/Gerber/EtchLayerBottom.gdo
    siemens-2/Gerber/GerberPlot.gpf
    siemens-2/Gerber/BoardOutlline.gdo
    upverter/design_export.gko
    upverter/design_export.gtl
    upverter/design_export.gbp
    upverter/design_export.gtp
    upverter/design_export.gbl
    upverter/design_export.gto
    upverter/design_export.gbs
    upverter/design_export.gts
    upverter/design_export.gbo
    eagle_files/solderpaste_bottom.gbr
    eagle_files/silkscreen_bottom.gbr
    eagle_files/profile.gbr
    eagle_files/copper_inner_l2.gbr
    eagle_files/copper_top_l1.gbr
    eagle_files/soldermask_top.gbr
    eagle_files/copper_inner_l3.gbr
    eagle_files/solderpaste_top.gbr
    eagle_files/soldermask_bottom.gbr
    eagle_files/copper_bottom_l4.gbr
    eagle_files/silkscreen_top.gbr
    diptrace/panel_BoardOutline.gbr
    diptrace/keyboard_BottomSilk.gbr
    diptrace/keyboard_Bottom.gbr
    diptrace/mainboard_Top.gbr
    diptrace/mainboard_TopMask.gbr
    diptrace/mainboard_BoardOutline.gbr
    diptrace/mainboard_Bottom.gbr
    diptrace/mainboard_BottomMask.gbr
    diptrace/keyboard_BottomMask.gbr
    diptrace/panel_Bottom.gbr
    diptrace/keyboard_BoardOutline.gbr
    diptrace/panel_BottomSilk.gbr
    diptrace/panel_BottomMask.gbr
    diptrace/mainboard_TopSilk.gbr
'''.splitlines() if l ]

MIN_REFERENCE_FILES = [
    'example_two_square_boxes.gbr',
    'example_outline_with_arcs.gbr',
    'example_flash_circle.gbr',
    'example_flash_polygon.gbr',
    'example_flash_rectangle.gbr',
    'example_simple_contour.gbr',
    'example_am_exposure_modifier.gbr',
    'bottom_copper.GBL',
    'bottom_silk.GBO',
    'eagle_files/copper_bottom_l4.gbr'
    ]

HAS_ZERO_SIZE_APERTURES = [
    'bottom_copper.GBL',
    'bottom_silk.GBO',
    'top_copper.GTL',
    'top_silk.GTO',
    'board_outline.GKO',
    'eagle_files/silkscreen_top.gbr',
    ]


@filter_syntax_warnings
@pytest.mark.parametrize('reference', REFERENCE_FILES, indirect=True)
def test_round_trip(reference, tmpfile):
    tmp_gbr = tmpfile('Output gerber', '.gbr')

    GerberFile.open(reference).save(tmp_gbr)

    mean, _max, hist = gerber_difference(reference, tmp_gbr, diff_out=tmpfile('Difference', '.png'))
    assert mean < 5e-5
    assert hist[9] == 0
    assert hist[3:].sum() < 5e-5*hist.size

@filter_syntax_warnings
@pytest.mark.parametrize('reference', REFERENCE_FILES, indirect=True)
def test_idempotence(reference, tmpfile):
    tmp_gbr_1 = tmpfile('First generation output', '.gbr')
    tmp_gbr_2 = tmpfile('Second generation output', '.gbr')

    GerberFile.open(reference).save(tmp_gbr_1)
    GerberFile.open(tmp_gbr_1).save(tmp_gbr_2)
    assert tmp_gbr_1.read_text() == tmp_gbr_2.read_text()


TEST_ANGLES = [90, 180, 270, 30, 1.5, 10, 360, 1024, -30, -90]
TEST_OFFSETS = [(0, 0), (100, 0), (0, 100), (2, 0), (10, 100)]

@filter_syntax_warnings
@pytest.mark.parametrize('reference', MIN_REFERENCE_FILES, indirect=True)
@pytest.mark.parametrize('angle', TEST_ANGLES)
def test_rotation(reference, angle, tmpfile):
    if 'flash_rectangle' in str(reference) and angle == 1024:
        # gerbv's rendering of this is broken, the hole is missing.
        pytest.skip()

    tmp_gbr = tmpfile('Output gerber', '.gbr')

    f = GerberFile.open(reference)
    f.rotate(math.radians(angle))
    f.save(tmp_gbr)

    cx, cy = 0, to_gerbv_svg_units(10, unit='inch')
    mean, _max, hist = gerber_difference(reference, tmp_gbr, diff_out=tmpfile('Difference', '.png'),
            svg_transform=f'rotate({angle} {cx} {cy})')
    assert mean < 1e-3 # relax mean criterion compared to above.
    assert hist[9] == 0

@filter_syntax_warnings
@pytest.mark.parametrize('reference', MIN_REFERENCE_FILES, indirect=True)
@pytest.mark.parametrize('angle', TEST_ANGLES)
@pytest.mark.parametrize('center', [(0, 0), (-10, -10), (10, 10), (10, 0), (0, -10), (-10, 10), (10, 20)])
def test_rotation_center(reference, angle, center, tmpfile):
    if 'flash_rectangle' in str(reference) and angle in (30, 1024):
        # gerbv's rendering of this is broken, the hole is missing.
        pytest.skip()

    tmp_gbr = tmpfile('Output gerber', '.gbr')

    f = GerberFile.open(reference)
    f.rotate(math.radians(angle), center=center)
    f.save(tmp_gbr)

    # calculate circle center in SVG coordinates 
    size = (10, 10) # inches
    cx, cy = to_gerbv_svg_units(center[0]), to_gerbv_svg_units(size[1], 'inch')-to_gerbv_svg_units(center[1], 'mm')
    mean, _max, hist = gerber_difference(reference, tmp_gbr, diff_out=tmpfile('Difference', '.png'),
            svg_transform=f'rotate({angle} {cx} {cy})',
            size=size)
    assert mean < 1e-3
    assert hist[9] < 50
    assert hist[3:].sum() < 1e-3*hist.size

@filter_syntax_warnings
@pytest.mark.parametrize('reference', MIN_REFERENCE_FILES, indirect=True)
@pytest.mark.parametrize('offset', TEST_OFFSETS)
def test_offset(reference, offset, tmpfile):
    tmp_gbr = tmpfile('Output gerber', '.gbr')

    f = GerberFile.open(reference)
    f.offset(*offset)
    f.save(tmp_gbr, settings=FileSettings(unit=f.unit, number_format=(4,7)))

    # flip y offset since svg's y axis is flipped compared to that of gerber
    dx, dy = to_gerbv_svg_units(offset[0]), -to_gerbv_svg_units(offset[1])
    mean, _max, hist = gerber_difference(reference, tmp_gbr, diff_out=tmpfile('Difference', '.png'),
            svg_transform=f'translate({dx} {dy})')
    assert mean < 1e-4
    assert hist[9] == 0

@filter_syntax_warnings
@pytest.mark.parametrize('reference', MIN_REFERENCE_FILES, indirect=True)
@pytest.mark.parametrize('angle', TEST_ANGLES)
@pytest.mark.parametrize('center', [(0, 0), (10, 0), (0, -10), (10, 20)])
@pytest.mark.parametrize('offset', [(0, 0), (100, 0), (0, 100), (100, 100), (100, 10)])
def test_combined(reference, angle, center, offset, tmpfile):
    if 'flash_rectangle' in str(reference) and angle in (30, 1024):
        # gerbv's rendering of this is broken, the hole is missing.
        pytest.skip()

    tmp_gbr = tmpfile('Output gerber', '.gbr')

    f = GerberFile.open(reference)
    f.rotate(math.radians(angle), center=center)
    f.offset(*offset)
    f.save(tmp_gbr, settings=FileSettings(unit=f.unit, number_format=(4,7)))

    size = (10, 10) # inches
    cx, cy = to_gerbv_svg_units(center[0]), to_gerbv_svg_units(size[1], 'inch')-to_gerbv_svg_units(center[1], 'mm')
    dx, dy = to_gerbv_svg_units(offset[0]), -to_gerbv_svg_units(offset[1])
    mean, _max, hist = gerber_difference(reference, tmp_gbr, diff_out=tmpfile('Difference', '.png'),
            svg_transform=f'translate({dx} {dy}) rotate({angle} {cx} {cy})',
            size=size)
    assert mean < 1e-3
    assert hist[9] < 100
    assert hist[3:].sum() < 1e-3*hist.size

@filter_syntax_warnings
@pytest.mark.parametrize('file_a', MIN_REFERENCE_FILES)
@pytest.mark.parametrize('file_b', [
    'example_two_square_boxes.gbr',
    'example_outline_with_arcs.gbr',
    'example_am_exposure_modifier.gbr',
    'bottom_silk.GBO',
    'eagle_files/copper_bottom_l4.gbr', ])
@pytest.mark.parametrize('angle', [0, 10, 90])
@pytest.mark.parametrize('offset', [(0, 0, 0, 0), (100, 0, 0, 0), (0, 0, 0, 100), (100, 0, 0, 100)])
def test_compositing(file_a, file_b, angle, offset, tmpfile, print_on_error):

    # TODO bottom_silk.GBO renders incorrectly with gerbv: the outline does not exist in svg. In GUI, the logo only
    # renders at very high magnification. Skip, and once we have our own SVG export maybe use that instead. Or just use
    # KiCAD's gerbview.
    # TODO check if this and the issue with aperture holes not rendering in test_combined actually are bugs in gerbv
    # and fix/report upstream.
    if file_a == 'bottom_silk.GBO' or file_b == 'bottom_silk.GBO':
        pytest.skip()

    ref_a = reference_path(file_a)
    print_on_error('Reference file a:', ref_a)
    ref_b = reference_path(file_b)
    print_on_error('Reference file b:', ref_b)

    ax, ay, bx, by = offset
    grb_a = GerberFile.open(ref_a)
    grb_a.rotate(math.radians(angle))
    grb_a.offset(ax, ay)

    grb_b = GerberFile.open(ref_b)
    grb_b.offset(bx, by)

    grb_a.merge(grb_b)
    tmp_gbr = tmpfile('Output gerber', '.gbr')
    grb_a.save(tmp_gbr, settings=FileSettings(unit=grb_a.unit, number_format=(4,7)))

    size = (10, 10) # inches
    ax, ay = to_gerbv_svg_units(ax), -to_gerbv_svg_units(ay)
    bx, by = to_gerbv_svg_units(bx), -to_gerbv_svg_units(by)
    # note that we have to specify cx, cy even if we rotate around the origin since gerber's origin lies at (x=0
    # y=+document size) in SVG's coordinate space because svg's y axis is flipped compared to gerber's.
    cx, cy = 0, to_gerbv_svg_units(size[1], 'inch')
    mean, _max, hist = gerber_difference_merge(ref_a, ref_b, tmp_gbr,
            composite_out=tmpfile('Composite', '.svg'), diff_out=tmpfile('Difference', '.png'),
            svg_transform1=f'translate({ax} {ay}) rotate({angle} {cx} {cy})',
            svg_transform2=f'translate({bx} {by})',
            size=size)
    assert mean < 1e-3
    assert hist[9] < 100
    assert hist[3:].sum() < 1e-3*hist.size

@filter_syntax_warnings
@pytest.mark.parametrize('reference', REFERENCE_FILES, indirect=True)
def test_svg_export(reference, tmpfile):
    if reference.name in ('silkscreen_bottom.gbr', 'silkscreen_top.gbr', 'top_silk.GTO'):
        # Some weird svg rendering artifact. Might be caused by mismatching svg units between gerbv and us. Result looks
        # fine though.
        pytest.skip()

    if reference.name == 'MinnowMax_assy.art':
        # This leads to worst-case performance in resvg, this testcase takes over 1h to finish. So skip.
        pytest.skip()

    grb = GerberFile.open(reference)

    bounds = (0.0, 0.0), (6.0, 6.0) # bottom left, top right

    out_svg = tmpfile('Output', '.svg')
    with open(out_svg, 'w') as f:
        f.write(str(grb.to_svg(force_bounds=bounds, arg_unit='inch', fg='black', bg='white')))

    # NOTE: Instead of having gerbv directly export a PNG, we ask gerbv to output SVG which we then rasterize using
    # resvg. We have to do this since gerbv's built-in cairo-based PNG export has severe aliasing issues. In contrast,
    # using resvg for both allows an apples-to-apples comparison of both results.
    ref_svg = tmpfile('Reference export', '.svg')
    ref_png = tmpfile('Reference render', '.png')
    gerbv_export(reference, ref_svg, origin=bounds[0], size=bounds[1], fg='#000000', bg='#ffffff')
    svg_to_png(ref_svg, ref_png, dpi=72, bg='white') # make dpi match Cairo's default

    out_png = tmpfile('Output render', '.png')
    svg_to_png(out_svg, out_png, dpi=72, bg='white') # make dpi match Cairo's default

    mean, _max, hist = image_difference(ref_png, out_png, diff_out=tmpfile('Difference', '.png'))
    assert mean < 1.2e-3
    assert hist[9] < 1
    assert hist[3:].sum() < 1e-3*hist.size

# FIXME test svg margin, bounding box computation

@filter_syntax_warnings
@pytest.mark.parametrize('reference', REFERENCE_FILES, indirect=True)
def test_bounding_box(reference, tmpfile):
    if reference.name == 'MinnowMax_assy.art':
        # This leads to worst-case performance in resvg, this testcase takes over 1h to finish. So skip.
        pytest.skip()
    # skip this check on files that contain lines with a zero-size aperture at the board edge
    if any(reference.match(f'*/{f}') for f in HAS_ZERO_SIZE_APERTURES):
        pytest.skip()

    margin = 1.0 # inch
    dpi = 200
    margin_px = int(dpi*margin) # intentionally round down to avoid aliasing artifacts

    grb = GerberFile.open(reference)

    if grb.is_empty:
        pytest.skip()

    out_svg = tmpfile('Output', '.svg')
    with open(out_svg, 'w') as f:
        f.write(str(grb.to_svg(margin=margin, arg_unit='inch', fg='white', bg='black')))

    out_png = tmpfile('Render', '.png')
    svg_to_png(out_svg, out_png, dpi=dpi)

    img = np.array(Image.open(out_png))
    img = img[:, :, :3].mean(axis=2) # drop alpha and convert to grayscale
    img = np.round(img).astype(int) # convert to int
    assert (img > 0).any() # there must be some content, none of the test gerbers are completely empty.
    cols = img.sum(axis=1)
    rows = img.sum(axis=0)
    col_prefix, col_suffix = np.argmax(cols > 0), np.argmax(cols[::-1] > 0)
    row_prefix, row_suffix = np.argmax(rows > 0), np.argmax(rows[::-1] > 0)
    print('cols:', col_prefix, col_suffix)
    print('rows:', row_prefix, row_suffix)

    # Check that all margins are completely black and that the content touches the margins. Allow for some tolerance to
    # allow for antialiasing artifacts and for things like very thin features.
    assert margin_px-2 <= col_prefix <= margin_px+2
    assert margin_px-2 <= col_suffix <= margin_px+2
    assert margin_px-2 <= row_prefix <= margin_px+2
    assert margin_px-2 <= row_suffix <= margin_px+2

@filter_syntax_warnings
def test_syntax_error():
    ref = reference_path('test_syntax_error.gbr')
    with pytest.raises(SyntaxError) as exc_info:
        GerberFile.open(ref)

    assert 'test_syntax_error.gbr' in exc_info.value.msg
    assert '7' in exc_info.value.msg # lineno