gistfile1.txt

- (void)fill:(int)button withColor:(NSColor*)fillColor {
    int imageSideLength = 72;
    NSImage *image = [[NSImage alloc] initWithSize:NSMakeSize(imageSideLength, imageSideLength)];
    [image lockFocus];
    [fillColor drawSwatchInRect:NSMakeRect(0, 0, imageSideLength, imageSideLength)];
    [image unlockFocus];

    //NSData *imageTiff = image.TIFFRepresentation;
    //NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:imageTiff];
    //NSData *data = [imageRep representationUsingType:NSBitmapImageFileTypeBMP properties:@{}];
    NSData *data = [image bmpData];

    int reportLength = 8191;
    uint8_t reportMagic[] = {0x02,  // Report ID
                             0x01,  // Unknown (always seems to be 1)
                             0x01,  // Image Page
                             0x00,  // Padding
                             0x00,  // Continuation Bool
                             button // Deck button to set
                            };

    int imageLen = (int)data.length;
    int halfImageLen = imageLen / 2;
    const uint8_t *imageBuf = data.bytes;

    // Prepare and send the first half of the image
    NSMutableData *reportPage1 = [NSMutableData dataWithLength:reportLength];
    [reportPage1 replaceBytesInRange:NSMakeRange(0, 6) withBytes:reportMagic];
    [reportPage1 replaceBytesInRange:NSMakeRange(16, halfImageLen) withBytes:imageBuf];
    const uint8_t *rawPage1 = (const uint8_t *)reportPage1.bytes;

    IOHIDDeviceSetReport(self.device, kIOHIDReportTypeOutput, rawPage1[0], rawPage1, reportLength);

    // Prepare and send the second half of the image
    NSMutableData *reportPage2 = [NSMutableData dataWithLength:reportLength];
    reportMagic[2] = 2;
    reportMagic[4] = 1;
    [reportPage2 replaceBytesInRange:NSMakeRange(0, 6) withBytes:reportMagic];
    [reportPage2 replaceBytesInRange:NSMakeRange(16, halfImageLen) withBytes:imageBuf+halfImageLen];
    const uint8_t *rawPage2 = (const uint8_t *)reportPage2.bytes;

    IOHIDDeviceSetReport(self.device, kIOHIDReportTypeOutput, rawPage2[0], rawPage2, reportLength);

}