RGBA16 pixel data

[SpiderPig]

How can I access the pixel data from a pixmap generated with TextureBuffer::Capture()?  I want to access the pixel data directly like this:

auto captures = texture_buffer->GetCaptures();
if (captures.size() != 0) {
    auto pixmap = captures[0];
    auto data = pixmap->pixels->Data();

    int x = 0, y = 0, stride = 4;
    auto i = ((y * pixmap->size.x) + x) * stride;

    auto r = data[0];
    auto g = data[1];
    auto b = data[2];
    auto a = data[3];
}

I've also tried this but it shows an error saying it "Bytes per block must be four or less"

auto pix = pixmap->ReadPixel(x, y);
auto r = Red(pix);
auto g = Green(pix);
auto b = Blue(pix);
auto a = Alpha(pix);

I can convert the pixmap from TEXTURE_RGB16 to TEXTURE_RGBA and both code will work but it's far too slow for my situation (I'm doing it once per frame).

 

[Josh]

Pixmap::Sample(). You can input an iVec2 to get a single pixel without bilinear filtering.

[SpiderPig]

Thanks.  It's actually 3 times slower to do that per pixel than to convert the whole pixmap and access the pixel data directly.

I am I correct in saying that for an RGBA16 format, the data here 2 bytes per channel?

char* data = pixmap->pixels->Data();

I need a value between 0 and 255 but I'm not positive if bit shifting like this is the right way.  And then I'm not positive how to get back the 0 - 255 range.

auto r = (data[index] << 8) | data[index + 1];
auto g = (data[index + 2] << 8) | data[index + 3];
auto b = (data[index + 4] << 8) | data[index + 5];
auto a = (data[index + 6] << 8) | data[index + 7];

index += 8;

 

[Josh]

Do it like this:
unsigned short* data = (unsigned short*)pixmap->pixels->Data();

Each channel will be a half float. Use halfToFloat() to convert that to a floating point number.

[SpiderPig]

Thanks that worked a treat.  Should we be able to change the format of a texturebuffer, like to RGBA or is RGBA16 the only one that will work for camera targets?

[Josh]

RGBA16 is used because it supports values outside the range of 0-1. This is important if post-processing effects are used, and it also important for environment probes.