No subimage when creating an image from scratch #261
Description
I'm unable to create an image from computed values.
For example (skipping error checks):
spng_ctx *ctx = spng_ctx_new(SPNG_CTX_ENCODER);
FILE *fp = fopen("my.png", "w");
spng_set_png_file(ctx, fp);
struct spng_ihdr ihdr = {0}; /* zero-initialize to set valid defaults */
ihdr.width = 400;
ihdr.height = 256;
ihdr.color_type = SPNG_COLOR_TYPE_TRUECOLOR;
ihdr.bit_depth = 8;
spng_set_ihdr(ctx, &ihdr); // this does not calculate subimage
size_t size = 4*400;
unsigned char *linebuf = malloc(size);
for (int i = 0; i < 256; ++i)
{
calculate_line_colors(linebuf);
ret = spng_encode_scanline(ctx, linebuf, size);
if(ret)
{
printf("spng_encode_scanline() error: %s\n", spng_strerror(ret));
goto encode_error;
}
}This prints "spng_encode_scanline() error: invalid buffer size" at line 4689 in spng.c as it checks len < (ctx->subimage[ctx->row_info.pass].scanline_width -1); scanline_width is 0, and subtracting 1 overflows.
If instead I call spng_encode_row() it prints "internal error", from line 4574 in spng.c, after it finds scanline_width to be 0.