BMP Color issue

[hipstersmoothie]

What's Changing and Why

bmp-js outputs the buffer in AGBR. This PR will convert bmp bitmap data to RGBA on encode and back to AGBR on encode. https://github.com/shaozilee/bmp-js

closes #521

pretty sure it also closes #432

What else might be affected

bmp file handling.

Tasks

• Add tests
• Update Documentation
• Update jimp.d.ts
• Add SemVer Label

[shawntabrizi]

@hipstersmoothie I believe I am running into this very issue right now using JIMP v0.9.3.

I read from a BMP, and make repeating writes to the file.

The writes are actually setting a batch of pixel values using the bitmap.setPixelColour(color, x, y); call.

What I notice is that every other write operation, the colors turn "red" like described in the issue. Then, the next write it turns back to normal.

I am wondering if the code somehow converts from AGBR -> RGBA and then back on a repating loop.