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