OpenGL GL_UNPACK_ALIGNMENT

Question

Before reading all this and getting lost, my main question is how to unpack a single array of pixels and explain how open gl reads this data. (my background is not in C ++, but mostly python)

Your help is greatly appreciated.

im using maya (a 3d program) that has a MImage class for obtaining pixel image data. the return result is one array in which every 4 elements are RGBA this is what I need to unpack

pixels = [255, 255, 0, 255, 255, 255, 0, 255] //two yellow pixels and it keeps going with this pattern

The following code creates a 256 x 256 image with 4 channels

unsigned int size = 256;
unsigned int depth = 4;

float color[3] = {1, 1, 0};

unsigned char *pixels = new unsigned char[size * size * depth];
for(unsigned int i = 0; i < size; i += depth){
    MScriptUtil::setUcharArray(pixels, i+0, (int)floorf(color[0] * 255.0f + 0.5f));
    MScriptUtil::setUcharArray(pixels, i+1, (int)floorf(color[1] * 255.0f + 0.5f));
    MScriptUtil::setUcharArray(pixels, i+2, (int)floorf(color[2] * 255.0f + 0.5f));
    pixels[i + 3] = 255;
    }

Studying this problem, I came across this fragment (which creates a validation template) that works with the last block of code and displays with what I'm trying to do

static GLubyte checkImage[256][256][4];

int i, j, c;

for (i = 0; i < 256; i++) {
    for (j = 0; j < 256; j++) {
        c = ((((i&0x8)==0)^((j&0x8))==0))*255;
        checkImage[i][j][0] = (GLubyte) c;
        checkImage[i][j][1] = (GLubyte) c;
        checkImage[i][j][2] = (GLubyte) c;
        checkImage[i][j][3] = (GLubyte) 255;
    }
}

this array becomes (instead of 256x256 I made it 2x2)

[[[255, 255, 255, 255], [255, 255, 255, 255]], [[255, 255, 255, 255], [255, 255, 255, 255]]]// so on and so forth

with this I set GL_UNPACK_ALIGNMENT to 1 and everything works

, gl

,

glDisable ( GL_LIGHTING );
glEnable(GL_TEXTURE_2D);


glGenTextures(1, &glTextureObject);

// set the current texture to the one just created
glBindTexture (GL_TEXTURE_2D, glTextureObject);

// repeat the texture in both directions
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

// use bi-linear filtering on the texture
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);


glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_REPLACE);

// load the texture data into the graphics hardware.
glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA, 256, 256, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

Answer 1

GL_UNPACK_ALIGNMENT . 4. 4 RGBA, 4.

, 4. , RGB 3 , 1, 4- .

, , - :

for(unsigned int i = 0; i < size; i += depth){
    MScriptUtil::setUcharArray(pixels, i+0, (int)floorf(color[0] * 255.0f + 0.5f));
    MScriptUtil::setUcharArray(pixels, i+1, (int)floorf(color[1] * 255.0f + 0.5f));
    MScriptUtil::setUcharArray(pixels, i+2, (int)floorf(color[2] * 255.0f + 0.5f));
    pixels[i + 3] = 255;
}

size 256, 256 ( 64 ) . , :

for(unsigned int i = 0; i < size * size * depth; i += depth) {