diff --git a/icoconvert.py b/icoconvert.py new file mode 100644 index 0000000..0740c4b --- /dev/null +++ b/icoconvert.py @@ -0,0 +1,243 @@ +# https://en.wikipedia.org/wiki/ICO_(file_format) + +# All values in ICO/CUR files are represented in little-endian byte order. + +# Broad file structure: +# _______________________ +# | ICO header | +# |-----------------------| +# | Icon directories 1..n | +# |-----------------------| +# | Image data 1..n | +# |_______________________| + +# ICO header: +# _______________________________________________________________________________ +# | Offset | Size (bytes) | Purpose | +# |--------|--------------|-------------------------------------------------------| +# | 0 | 2 | Reserved. Must always be 0. | +# |--------|--------------|-------------------------------------------------------| +# | 2 | 2 | Specifies image type: 1 for icon (.ICO) image, | +# | | | 2 for cursor (.CUR) image. Other values are invalid. | +# |--------|--------------|-------------------------------------------------------| +# | 4 | 2 | Specifies number of images in the file. | +# |________|______________|_______________________________________________________| + +# Icon directory structure: +# _______________________________________________________________________________ +# | Offset | Size (bytes) | Purpose | +# |--------|--------------|-------------------------------------------------------| +# | 0 | 1 | Specifies image width in pixels. Can be any number | +# | | | between 0 and 255. Value 0 means image width is 256 | +# | | | pixels. | +# |--------|--------------|-------------------------------------------------------| +# | 1 | 1 | Specifies image height in pixels. Can be any number | +# | | | between 0 and 255. Value 0 means image height is 256 | +# | | | pixels. | +# |--------|--------------|-------------------------------------------------------| +# | 2 | 1 | Specifies number of colors in the color palette. | +# | | | Should be 0 if the image does not use a color palette | +# |--------|--------------|-------------------------------------------------------| +# | 3 | 1 | Reserved. Should be 0. | +# |--------|--------------|-------------------------------------------------------| +# | 4 | 2 | In ICO format: Specifies color planes. | +# | | | Should be 0 or 1. | +# | | | In CUR format: Specifies the horizontal coordinates | +# | | | of the hotspot in number of pixels from the left. | +# |--------|--------------|-------------------------------------------------------| +# | 6 | 2 | In ICO format: Specifies bits per pixel. | +# | | | In CUR format: Specifies the vertical coordinates of | +# | | | the hotspot in number of pixels from the top. | +# |--------|--------------|-------------------------------------------------------| +# | 8 | 4 | Specifies the size of the image's data in bytes | +# |--------|--------------|-------------------------------------------------------| +# | 12 | 4 | Specifies the offset of BMP or PNG data from the | +# | | | beginning of the ICO/CUR file | +# |________|______________|_______________________________________________________| + +# Image data structure +# BMP, starting from the BITMAPINFOHEADER, ignoring normal file header: +# _______________________________________________________________________________ +# | Offset | Size (bytes) | Purpose | +# |--------|--------------|-------------------------------------------------------| +# | 0 | 4 | The size of this header. Always 40. | +# |--------|--------------|-------------------------------------------------------| +# | 4 | 4 | Image width in pixels, signed. | +# |--------|--------------|-------------------------------------------------------| +# | 8 | 4 | Image height in pixels, signed. | +# |--------|--------------|-------------------------------------------------------| +# | 12 | 2 | Number of color planes. Always 1. | +# |--------|--------------|-------------------------------------------------------| +# | 14 | 2 | Bits per pixel aka color depth. | +# |--------|--------------|-------------------------------------------------------| +# | 16 | 4 | Compression method. 0 for None aka BI_RGB. | +# |--------|--------------|-------------------------------------------------------| +# | 20 | 4 | Image bytes length. 0 for BI_RGB because inferred. | +# |--------|--------------|-------------------------------------------------------| +# | 24 | 4 | Horizontal print resolution. | +# |--------|--------------|-------------------------------------------------------| +# | 28 | 4 | Vertical print resolution | +# |--------|--------------|-------------------------------------------------------| +# | 32 | 4 | Number of colors in palette. 0 for 2^n. | +# |--------|--------------|-------------------------------------------------------| +# | 36 | 4 | Number of important colors. 0 for all. | +# |--------|--------------|-------------------------------------------------------| +# | 40 | n | Pixel bytes, r, g, b, a. | +# |________|______________|_______________________________________________________| + +import os +import sys +from PIL import Image + + +ICO_HEADER_LENGTH = 6 +ICON_DIRECTORY_ENTRY_LENGTH = 16 +BMP_HEADER_LENGTH = 40 + + +def chunk_sequence(sequence, chunk_length, allow_incomplete=True): + ''' + Given a sequence, divide it into sequences of length `chunk_length`. + + allow_incomplete: + If True, allow the final chunk to be shorter if the + given sequence is not an exact multiple of `chunk_length`. + If False, the incomplete chunk will be discarded. + ''' + (complete, leftover) = divmod(len(sequence), chunk_length) + if not allow_incomplete: + leftover = 0 + + chunk_count = complete + min(leftover, 1) + + chunks = [] + for x in range(chunk_count): + left = chunk_length * x + right = left + chunk_length + chunks.append(sequence[left:right]) + + return chunks + +def fit_into_bounds(iw, ih, fw, fh): + ''' + Given the w+h of the image and the w+h of the frame, + return new w+h that fits the image into the frame + while maintaining the aspect ratio and leaving blank space + everywhere else + ''' + ratio = min(fw/iw, fh/ih) + + w = int(iw * ratio) + h = int(ih * ratio) + return (w, h) + +def little(x, length): + return x.to_bytes(length, byteorder='little') + +def load_image(filename): + image = Image.open(filename) + if min(image.size) > 256: + (w, h) = image.size + image = image.resize(fit_into_bounds(w, h, 256, 256), resample=Image.ANTIALIAS) + image = image.convert('RGBA') + return image + +def build_ico_header_blob(image_count): + datablob = (b'' + + little(0, 2) # reserved + + little(1, 2) # 1 = ico type + + little(image_count, 2) + ) + return datablob + +def build_icon_directory_blob(image, offset_from_start): + (width, height) = image.size + datablob = (b'' + + little(width if width < 256 else 0, 1) + + little(height if height < 256 else 0, 1) + + little(0, 1) # colors in palette + + little(0, 1) # reserved + + little(1, 2) # color planes + + little(32, 2) # bit depth + + little((width * height * 4) + BMP_HEADER_LENGTH, 4) # image bytes length + + little(offset_from_start, 4) + ) + return datablob + +def build_image_data_blob(image): + datablob = (b'' + + little(40, 4) # header size + + little(image.size[0], 4) + # "Even if the AND mask is not supplied, if the image is in Windows BMP + # format, the BMP header must still specify a doubled height." - wikipedia + + little(image.size[1] * 2, 4) + + little(1, 2) # color planes + + little(32, 2) # bit depth + + little(0, 4) # no compression + + little(0, 4) # bytes length, inferred + + little(0, 4) # hor print + + little(0, 4) # ver print + + little(0, 4) # palette + + little(0, 4) # important palette + ) + pixeldata = [] + # Image.getdata() is a list of (r, g, b, a) channels + # But the BMP are written (b, g, r, a) + # Also they are written from bottom to top. + pixels = list(image.getdata()) + pixels = reversed(chunk_sequence(pixels, image.size[0])) + pixels = [line for chunk in pixels for line in chunk] + for pixel in pixels: + (r, g, b, a) = pixel + pixeldata.extend((b, g, r, a)) + datablob += bytes(pixeldata) + return datablob + +def images_to_ico(images): + # For some reason Windows reads the icons in reverse order. + images.reverse() + + # The directory entries need to know their image's address, so therefore + # we must know the lengths of all the image binaries before we can write + # any directory entries. + # We will calculate the image blobs first, store them separately, + # and then put them after the directory blobs. + datablobs = [] + imageblobs = [] + + ico_header_blob = build_ico_header_blob(image_count=len(images)) + datablobs.append(ico_header_blob) + + for (index, image) in enumerate(images): + imageblob = build_image_data_blob(image) + imageblobs.append(imageblob) + + # Since the ICO header and directory entries are of fixed length, we know + # the location of the first image. + # After that, the offset just gains the size of the previous image. + offset_from_start = ICO_HEADER_LENGTH + (len(images) * ICON_DIRECTORY_ENTRY_LENGTH) + for (index, (image, imageblob)) in enumerate(zip(images, imageblobs)): + directoryblob = build_icon_directory_blob(image, offset_from_start=offset_from_start) + datablobs.append(directoryblob) + offset_from_start += len(imageblob) + + datablobs.extend(imageblobs) + + final_data = b''.join(datablobs) + return final_data + + +if __name__ == '__main__': + try: + inputfiles = sys.argv[1:] + except: + print('Please provide an image file') + raise SystemExit + print('Iconifying', inputfiles) + images = [load_image(filename) for filename in inputfiles] + final_data = images_to_ico(images) + name = os.path.splitext(inputfiles[0])[0] + '.ico' + output_file = open(name, 'wb') + output_file.write(final_data) + output_file.close() + print('Finished %s.' % name)