.Net Bitmap class constructor (int, int) and (int, int, PixelFormat) throws ArgumentException on perfectly good arguments

Question

I have some code that does something like this (Irrelevant bits snipped):

void foo(Bitmap bmp1, Bitmap bmp2)
{
    Bitmap bmp3;
    if(something)
        bmp         


        

Answer 1

GDI+ does not generate very good exception messages. The exception you got is flaky, this one will generate it reliably on my machine:

    private void button1_Click(object sender, EventArgs e) {
        var bmp = new Bitmap(20000, 20000);
    }

What's really going on is that this bitmap requires too much contiguous unmanaged memory to store the bitmap bits, more than is available in your process. On a 32-bit operating system, you can only ever hope to allocate a chunk of memory around 550 megabytes. That goes quickly down-hill from there.

The issue is address space fragmentation, the virtual memory of your program stores a mix of code and data at various addresses. Total memory space is around 2 gigabytes but the biggest hole is much smaller than that. You can only consume all memory with lots of small allocations, big ones fail much quicker.

Long story short: it is trying to tell you that the size you requested cannot be supported.

A 64-bit operating system doesn't have this problem. Be sure to take advantage of it with Project > Properties > Build tab, Platform target = AnyCPU and Prefer 32-bit = unticked. Also, WPF relies on WIC, an imaging library that's a lot smarter about allocating buffers for bitmaps.

Answer 2

Check whether bmp1 or bmp2 has been Disposed (even if not null). See here:

The Mysterious Parameter Is Not Valid Exception

Answer 3

Anyone have any ideas?

Wrap the call that is throwing ArgumentException with a try-catch(Exception ex) and step into the exception block to see the raw exception. It should give you more detail, like which argument is supposedly invalid.

try
{
    bmp3 = new Bitmap(bmp1.Width, bmp1.Height + bmp2.Height);
}
catch (Exception ex)
{   
    throw;  // breakpoint here, examine "ex"
}