I understand you guys are programmers so I totally understand you are used to counting from 0, as in 10 is 0-9. but on the PNG export there are several mistakes that should be cleared up.
1. If the program asks how many images you want Spriter to divide your animation into, you should get that number of images.
Under keyframes to output, the first field reads "images". if you put in 16, you get 17. 0-16. should be 16, 0-15 if you want to count from 0.
2. under source rectangle > custom rectangle, you have left, top, right, bottom. I understand you are used to counting the points, rather than the space between, but in this situation, I don't believe 0 should be counted.
Entering a left of -64 and a right of 64 shows a width: 129
Entering a top of -128 and a bottom of 0 shows a height: 129
I tested this with an image output at -127 top and 0.0 bottom, and the output image was 128px tall.
I believe it should be from 0 to 1 is 1 pixel, from 1 to 2 is 2 pixels ... from 127 to 128 is 128 pixels.
I also checked to make sure it was not something with it flipping from positive to negative, by setting 0 top and 128 bottom, and still showed 129 height. Considering the previous test, this would output a 129px height image.
I could be entirely wrong here, but it just seems to me that the math should not be counting 0 for measurements of image width/height. I understand the reasoning for numbering the output images this way, as many languages have their lists and arrays set to begin counting at 0, so it might be useful on the series of images, but I don't think it's as useful in the png export.
Just my feedback from using the app. still a wonderful tool and I am enjoying using it a lot.
Thank you and keep up the great work!