Render.m

// The plain image data is stored in `bitmap`
NSInteger samplesPerPixel = [bitmap samplesPerPixel];
int rowLength = 0;
int unpackAlign = 0;

// Save original value temporary
glGetIntegerv(GL_UNPACK_ROW_LENGTH, &rowLength);
glGetIntegerv(GL_UNPACK_ALIGNMENT, &unpackAlign);

// Calculate and store necessary values for texture
glPixelStorei(GL_UNPACK_ROW_LENGTH, (int)[bitmap bytesPerRow] / samplesPerPixel);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

// `textureId` is passed from Unity
glBindTexture(GL_TEXTURE_2D, textureId);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

if (![bitmap isPlanar] &&
    (samplesPerPixel == 3 || samplesPerPixel == 4)) {
    glTexImage2D(GL_TEXTURE_2D,
                0,
                samplesPerPixel == 4 ? GL_RGBA8 : GL_RGB8,
                (int)[bitmap pixelsWide],
                (int)[bitmap pixelsHigh],
                0,
                samplesPerPixel == 4 ? GL_RGBA : GL_RGB,
                GL_UNSIGNED_BYTE,
                [bitmap bitmapData]);
}

// Restore values
glPixelStorei(GL_UNPACK_ROW_LENGTH, rowLength);
glPixelStorei(GL_UNPACK_ALIGNMENT, unpackAlign);