Save RGB values to jpeg use libjpeg, getting weird results - c++

Question

I have a program that will load a jpeg image and allow the user to draw on the image and resave it.
I have loading and drawing working, but when I try to save the image I get this result
The result should have just been the image of the snail with the line.
Here is my code
bool IOManager::save_jpg_to_file(const char *file_name) {
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr jerr;
FILE * outfile;
JSAMPROW row_pointer[1];
int row;
JSAMPLE * image_buffer;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
if ((outfile = fopen(file_name_.c_str(), "wb")) == NULL) {
fprintf(stderr, "can't open %s\n", file_name_);
return false;
}
jpeg_stdio_dest(&cinfo, outfile);
int img_width = pixel_buffer_->width();
int img_height = pixel_buffer_->height();
cinfo.image_width = img_width;
cinfo.image_height = img_height;
cinfo.input_components = 3;
cinfo.in_color_space = JCS_RGB;
jpeg_set_defaults(&cinfo);
jpeg_set_quality(&cinfo, 100, TRUE);
jpeg_start_compress(&cinfo, TRUE);
unsigned char bytes[img_width * 3];
while (cinfo.next_scanline < cinfo.image_height) {
for (int i = 0; i < img_width; i+=3){
ColorData colorData = pixel_buffer_->get_pixel(i, cinfo
.next_scanline);
bytes[i] = static_cast<int>(colorData.red()*255) & 0xff;
bytes[i+1] = static_cast<int>(colorData.green()*255) & 0xff;
bytes[i+2] = static_cast<int>(colorData.blue()*255) & 0xff;
}
row_pointer[0] = bytes;
(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
}
jpeg_finish_compress(&cinfo);
fclose(outfile);
jpeg_destroy_compress(&cinfo);
std::cout << "Done" << std::endl;
return true;
}
PixelBuffer is just a 2D array of RGB values.
I cannot figure out why it is generating those weird line, any help?

Answer 1

Just posting my comment as a separate answer. You seem to be accessing your pixel buffer data in a wrong way: you are jumping over 3 pixels in both source and destination buffer, while (given your code fragment) it looks like you need to process every pixel of your source. Make sure you increment index only by 1 not 3 when iterating pixel_buffer_