XFA: Support PNG format in pdfium_test and add image diffing

XFA: Support PNG format in pdfium_test and add image diffing

Lays the groundwork for pixel-diffing tests in pdfium.

This is a port of chromium's tools/image_diff/image_diff_png.cc onto the
top of the fxcodec-provided version of libpng. pdfium_test is modified
to support the new format, and the tools/image_diff.cc image comparison
utility is provided, stripped of its base/ dependencies.

Unfortunately, this can't be back-ported to origin/main, since the
underlying PNG support isn't present inside pdfium.

BUG=https://code.google.com/p/pdfium/issues/detail?id=62
R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/af18cb3e7c89d4b6b93765d0f3e5ae6e2e0d8163

[Tom Sepez, 2015-02-05 00:34:24]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-02-05 00:49:58]

Lei, please review.

[Tom Sepez, 2015-02-05 18:33:51]

tsepez@chromium.org changed reviewers:
+ jam@chromium.org

[Tom Sepez, 2015-02-05 18:35:15]

+jam, if you've got good ideas about how to do things cleanly here.

[jam, 2015-02-05 21:24:00]

On 2015/02/05 18:35:15, Tom Sepez wrote:
> +jam, if you've got good ideas about how to do things cleanly here.

anything in particular you want me to look at? I looked at this briefly and
didn't see anything off.

[Tom Sepez, 2015-02-05 21:38:51]

> anything in particular you want me to look at? I looked at this briefly and
> didn't see anything off.
No, just your blessing as to whether the overall approach is workable.

[Lei Zhang, 2015-02-05 22:11:08]

Sounds like a plan.

https://codereview.chromium.org/870203005/diff/20001/samples/BUILD.gn
File samples/BUILD.gn (right):

https://codereview.chromium.org/870203005/diff/20001/samples/BUILD.gn#newcode14
samples/BUILD.gn:14: "image_diff_png.cc",
nit: alphabetical order, ditto elsewhere.

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.cc
File samples/image_diff_png.cc (right):

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.c...
samples/image_diff_png.cc:39: FORMAT_SkBitmap
Remove

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.h
File samples/image_diff_png.h (right):

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.h...
samples/image_diff_png.h:8: #include <string>
not needed

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc
File samples/pdfium_test.cc (right):

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc#n...
samples/pdfium_test.cc:161: if (stride < 0 || width < 0 || height < 0)
We do the same checks in every version of WriteFoo(). Consolidate them into a
function?

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc#n...
samples/pdfium_test.cc:175: snprintf(filename, sizeof(filename), "%s.%d.png",
pdf_name, num);
Check the return value?

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc#n...
samples/pdfium_test.cc:183: size_t bytes_written = fwrite(&png_encoding.front(),
1, png_encoding.size(), fp);
over 80 chars / line

https://codereview.chromium.org/870203005/diff/20001/samples/samples.gyp
File samples/samples.gyp (right):

https://codereview.chromium.org/870203005/diff/20001/samples/samples.gyp#newc...
samples/samples.gyp:22: 'target_name': 'pdfium_diff',
Not building this for GN?

[Tom Sepez, 2015-02-05 22:58:21]

https://codereview.chromium.org/870203005/diff/20001/samples/BUILD.gn
File samples/BUILD.gn (right):

https://codereview.chromium.org/870203005/diff/20001/samples/BUILD.gn#newcode14
samples/BUILD.gn:14: "image_diff_png.cc",
On 2015/02/05 22:11:08, Lei Zhang wrote:
> nit: alphabetical order, ditto elsewhere.

Done.

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.cc
File samples/image_diff_png.cc (right):

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.c...
samples/image_diff_png.cc:39: FORMAT_SkBitmap
On 2015/02/05 22:11:08, Lei Zhang wrote:
> Remove

Done.

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.h
File samples/image_diff_png.h (right):

https://codereview.chromium.org/870203005/diff/20001/samples/image_diff_png.h...
samples/image_diff_png.h:8: #include <string>
On 2015/02/05 22:11:08, Lei Zhang wrote:
> not needed

Done.

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc
File samples/pdfium_test.cc (right):

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc#n...
samples/pdfium_test.cc:175: snprintf(filename, sizeof(filename), "%s.%d.png",
pdf_name, num);
On 2015/02/05 22:11:08, Lei Zhang wrote:
> Check the return value?

Done.

https://codereview.chromium.org/870203005/diff/20001/samples/pdfium_test.cc#n...
samples/pdfium_test.cc:183: size_t bytes_written = fwrite(&png_encoding.front(),
1, png_encoding.size(), fp);
On 2015/02/05 22:11:08, Lei Zhang wrote:
> over 80 chars / line

Done.

https://codereview.chromium.org/870203005/diff/20001/samples/samples.gyp
File samples/samples.gyp (right):

https://codereview.chromium.org/870203005/diff/20001/samples/samples.gyp#newc...
samples/samples.gyp:22: 'target_name': 'pdfium_diff',
On 2015/02/05 22:11:08, Lei Zhang wrote:
> Not building this for GN?
Good catch.

[Lei Zhang, 2015-02-05 23:05:19]

lgtm

[Tom Sepez, 2015-02-05 23:06:09]

Committed patchset #4 (id:60001) manually as
af18cb3e7c89d4b6b93765d0f3e5ae6e2e0d8163 (presubmit successful).