Image libraries writing incorrectly - c++

Question

I am using libpng and libjpeg to read and write images. The code I use was taken almost straight from the examples provided with the two libraries' documentation, and image loading works correctly with both libraries. However, when I go to save an image, something goes wrong, and it seems to write corrupted data somehow. The confusing part is that it writes it in exactly the same incorrect way, using both libraries. Here's an example:
Original:
Blurred picture (as it looks in the program, before saving):
How it saves (png):
The jpeg version saves with identical discoloration, just more compressed.
Here's the png saving code:
void PNGHandler::save(PixelBuffer* buffer, std::string fileName)
{
FILE* filePointer = fopen(fileName.c_str(), "wb");
int width = buffer->getWidth();
int height = buffer->getHeight();
png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
png_infop info = png_create_info_struct(png);
png_init_io(png, filePointer);
// 8-bit depth, RGBA
png_set_IHDR(png, info, width, height, 8,
PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_write_info(png, info);
// Set up rows for writing from
png_bytep *rowPointers = new png_bytep[height];
for(int y = 0; y < height; y++) {
rowPointers[y] = new png_byte[png_get_rowbytes(png,info)];
}
for(int y = 0; y < height; y++) {
for(int x = 0; x < width; x++) {
ColorData cd = buffer->getPixel(x, height - y - 1);
rowPointers[y][x*4] = (int)(cd.getRed() * 255);
rowPointers[y][x*4+1] = (int)(cd.getGreen() * 255);
rowPointers[y][x*4+2] = (int)(cd.getBlue() * 255);
rowPointers[y][x*4+3] = (int)(cd.getAlpha() * 255);
}
}
png_write_image(png, rowPointers);
png_write_end(png, info);
delete [] rowPointers;
png_destroy_write_struct(&png, &info);
fclose(filePointer);
}
(I know the error handling isn't great right now, but I'll fix that later)
Additionally, the file always saves this way. That is, I can apply the blur and save, then reload the original and do it again, and performing a diff on the two files reveals they're identical. The PixelBuffer pointer that's passed in is a pointer to the buffer that is being displayed on the screen, so all of the color data should be exactly as it appears.
I know this isn't much information to go on, but if someone can guide me toward what I should look for, I can bring more to the table (it's a large project, so I can't post all the code)
Edit: It's also worth noting that the image looks correct after saving, but once the saved image is loaded in, it displays the discoloration. This points toward a problem in the saving methods to me

Answer 1

Your filter/blur probably overflows/underflows the color values. You should make sure that the values are saturated within 0 and 255 (if values goes under 0, set them to 0, and if values goes above 255, set them to 255)